The family’s illustrious descent
Eustace II of Boulogne
Ida, the wife of Herman van Malsen and founding mother of the van Cuyck family, was the daughter of Eustace II and Ida of Boulogne. Both her parents came from important families. Her father Eustace was born around 1015-1022. He was the eldest son of Count Eustace I of Boulogne (1024-1047) and Matilda of Louvain († 1049), daughter of Count Lambert I of Louvain (1003-1015) and Gerberga of Lower Lorraine († 1018). After his father’s death in 1047, Eustace II inherited the county of Boulogne, while the county of Lens went to his younger brother Lambert. Eustace II later also inherited Lens, when Lambert’s son was killed in battle in 1054.
The maternal and paternal ancestry of Count Eustace II was impressive. His mother, Matilda of Louvain, was a granddaughter of Charles of Lorraine (977-993), the last lineal male descendant of Charlemagne. Eustace’s father also descended from Charlemagne through the marriage of the emperor’s great-granddaughter Judith with Baldwin I, count of Flanders (863-879). Eustace’s dual Carolingian bloodline was the richest of any of his contemporaries and it gave him a lustre that was widely recognized. In the 11th century, the blood of Charlemagne was highly praised. The famous English chronicler Orderic Vitalis calls Eustace II a man of the very highest birth, sprung from the stock of Charlemagne, most renowned king of the Franks. Through his father, Eustace also descended from King Alfred the Great (871-899) through the marriage of the latter’s daughter Elftrudis with Baldwin II, count of Flanders (879-918).
Eustace’s brother Godfrey was bishop of Paris. His other brother, Lambert, married the daughter of Robert I, duke of Normandy (1027-1035).
In the early 1080s, a genealogy of the Boulonnais dynasty was produced which stressed Eustace's dual Carolingian descent, his marriage to the illustrious Ida of Lorraine, and also reflected the prestige the family had gained through Eustace's military prowess. According to this contemporary Genealogia Comitum Boloniensium, Eustace descended – via Charlemagne and the Merovingian kings – from King Priam of Troy.
In 1035, Eustace II married Goda or Godgifu, daughter of the English King Æthelred the Unready (978/9-1016) and his second wife Emma of Normandy. This marriage provided the county of Boulogne with two important alliances. Goda was the widow of Drogo of Mantes, count of Amiens-Vexin (1027-1035). Eustace thus sealed an alliance with his stepsons: Ralph, count of Hereford († 1057), and Walter III, count of Vexin and Amiens (1035-1063). And when Goda’s brother Edward the Confessor became king of England in 1042, Eustace became his loyal ally. But Goda was also related to the duke of Normandy, her mother Emma being a daughter of Richard I of Normandy (942-996). Thus Eustace had strong family ties to both England and Normandy. Through Goda, Eustace also acquired interests in a considerable amount of landed property in England.
About 1049, after Goda’s death, Eustace married Ida, daughter of Godfrey II the Bearded (1044-1069), duke of Upper Lorraine, and Doda or Uoda. Ida’s family was amongst the most distinguished and influential in Germany.
Eustace and 1066
In August or September 1051 Eustace travelled to England to discuss matters with King Edward the Confessor. It is likely that Eustace conferred with Edward about the latter’s succession. The king’s marriage to Edith of Wessex had remained childless and he was making preparations to appoint a successor. Eustace probably advocated the claims of his stepsons (the sons of his wife and Edwards sister Godgifu and her first husband Drogo of Mantes, count of the Véxin). On his return, an armed conflict broke out between Eustace’s party and the citizens of Dover. As the different sources contradict each other, the circumstances of this incident are not clear. In any case, Godwin of Wessex, the most powerful earl of England (and father-in-law of Edward the Confessor), refused to punish the town of Dover and Eustace prepared himself for battle against Godwin and his supporters. King Edward, however, sought a peaceful solution through a trial of Godwin and his sons, the affair resulting in the banishment of Godwin and his family. Eustace maintained friendly relations with King Edward, while he became an enemy of Earl Godwin and his sons.
Eustace played a significant role at the Battle of Hastings in 1066, as is clear from the wealth attributed to him in Domesday Book. His martial deeds are commemorated in the Carmen de Hastingae Proelio and the Bayeux Tapestry. In the Carmen, he is even mentioned as one of the killers of Harold.
Eustace returned to the Continent in 1067, but that same year he led an attack on Dover. More specifically he attacked Dover castle, which William entrusted to his half-brother Odo, Bishop of Bayeux. It was a well-planned attack, timed to coincide with the absence of Odo and his knights. Although Eustace had the support from a large contingent from the nearby regions, the knights were scattered. A kinsman of Eustace was captured, but Eustace himself managed to escape and returned to Boulogne. In the end the attempt to seize Dover was a disaster: a close kinsman of Eustace was taken prisoner, the count himself was condemned and his lands in England were forfeited.
A few years later Eustace reached reconciliation with William the Conqueror and was granted an enormous English lordship. After William’s father-in-law, Count Baldwin V of Flanders, died in 1067, he was looking for a strong ally in the region. In 1071 Eustace and William both supported Arnulf III, the minor count of Flanders, and his mother and guardian Richilde of Hainault, against the usurper Robert the Frisian. When the latter allied himself with Philip I of France, William certainly needed Eustace to protect the northern border of his duchy. Moreover it was very convenient for William to be able to use the short sea crossing from Wissant to Dover. And lastly Eustace’s brother Geoffrey, Bishop of Paris and chancellor to the French king, could have been an interesting contact for William. As for Eustace, William was an important ally in his aim to maintain and enhance his independence from Flanders. The reconciliation certainly took place before 1086: in that year Eustace was the tenth richest landholder recorded in Domesday Book.
Eustace and the Bayeux Tapestry
The Bayeux Tapestry is a beautifully embroidered piece of linen of about 70 meters long and 50 centimetres high, depicting the story of Harold Godwinson and William the Bastard, duke of Normandy, and the succession of the English throne in 1066. From the 18th century onwards, the Tapestry was known as La Tapisserie de la Reine Mathilde (The Tapestry of Queen Mathilda). People believed that the embroidery was the work of Queen Mathilda, William the Conqueror’s wife: while her husband was away to conquer England, Mathilda filled her long and lonely evenings embroidering the Tapestry.
Scholars have long since abandoned the belief that the Tapestry was embroidered or even commissioned by Queen Mathilda, and for a long time it was widely accepted that Bishop Odo of Bayeux, William the Conqueror’s half-brother, was the most likely patron of the work.
Odo of Bayeux certainly is a good candidate. The Tapestry gives him a prominent place in the story, greater than other contemporary sources. According to the Tapestry, Harold took his oath in favour of William at Odo’s cathedral city of Bayeux. Two minor characters named in the Tapestry, Wadard and Vital, can be identified as tenants of Odo in post-Conquest Kent. Moreover, the Tapestry has long been connected with the Cathedral of Bayeux. Since the Tapestry shows various characteristics of English design and manufacture, it could have been made in Kent, Odo’s power base in England after the Conquest, perhaps at St. Augustine’s in Canterbury.
It is widely accepted that the Tapestry does not represent the most authentic, most aggressive point of view of the events. The work is sympathetic to the memory of Harold, who is not at all depicted as the villain and cruel murderer the chronicler William of Poitiers makes him out to be. In the written sources, Odo is described as an extremely ambitious person whose attitude toward the defeated English was at best one of disdain and at worst one of outright cruelty. The contradiction between the Tapestry’s version of events and Odo’s attitude toward the English creates some doubt as to the bishop’s patronage of the embroidery.
Eustace II seems the more likely candidate as patron of the Tapestry.  The count was one of William’s most powerful and prestigious non-Norman allies at Hastings and he takes a prominent place in the Tapestry. At a crucial moment in the battle, he turns around to point to Duke William as the latter raises his nosepiece to dispel rumours of his death. Since we know that Eustace rebelled against the Normans in 1067 by attacking Dover castle, it is odd that Eustace should take such a prominent place in the Tapestry. In fact it is odd that he is depicted at all, if indeed the Tapestry was commissioned by the bishop of Bayeux. But knowing that Dover castle in fact belonged to Odo who is also given a prominent place in the Tapestry, we may assume that Eustace was the Tapestry’s patron and that it was intended as a gift from Eustace to Odo, and as such formed part of the process of their reconciliation after the Dover attack. In any case, the choice of Odo and Eustace as the only named battle companions of the Conqueror attests to the fact that the relation between them was a fundamental reason for the creation of the Tapestry. Susan Brown believes that the sequential arrangement of the chosen highlights of the Battle of Hastings in the Bayeux Tapestry was carefully orchestrated so as to present the ultimate French victory as a direct result of an action that originated in the alliance between Odo of Bayeux, William the Conqueror and Eustace II of Boulogne.
There are other elements underlying the importance of Eustace in the Tapestry. His name is captioned as a single word in the upper border. Eustace’s banner is the largest and most elaborate one in the whole Tapestry. And the archer depicted directly below Eustace is the only coloured one. All these elements draw the eye to the count of Boulogne.
On the Bayeux Tapestry, Eustace is holding a banner in his hands. It is the largest banner on the Tapestry and several scholars believe this to be the famous papal banner. According to William of Poitiers, Pope Alexander II blessed William’s expedition and sent a papal banner that was borne at Hastings together with a ring containing a hair of Saint Peter. According to Orderic Vitalis, however, this banner was borne by Turstin, the son of Rollo.
The banner is an element to help identify the figure holding it. The device on the banner – a cross shape cantoned by four disks – can be found on Eustace’s coinage, but also on a large variety of early medieval coinage throughout Europe. More convincing is the similarity between the device on the banner and the symbol used to identify Saint Eustachius in medieval times. Saint Eustachius was converted to Christianity after receiving a vision: while he was hunting a stag, he saw a cross between the stag’s antlers. The drawing on the banner in the Tapestry can be seen as a stylized representation of the cross in the stag’s antlers. The disks may also refer to the coat of arms of the county of Boulogne.
The Bayeux Tapestry confirms the important role Eustace played in the Battle of Hastings. Without Eustace and his knights, the battle might have been lost for William. The climax of the battle was, of course, the death of Harold. On the Tapestry we can see that Harold is struck in the eye by an arrow; he is slain in the next scene by a knight with a sword.
According to the Carmen de Hastingae Proelio, Harold was attacked by William, Eustace of Boulogne, Hugh of Ponthieu, and Walter Giffard: these four bore arms for the destruction of the king. Each of these four delivers a mortal blow to Harold: The first of the four [Duke William of Normandy], piercing the king’s shield and chest with his lance, drenched the ground with a gushing stream of blood. The second [Count Eustace of Boulogne] with his sword cut off his head below the protection of his helm. The third [Hugh of Ponthieu] liquefied his entrails with his spear. And the fourth [Walter Giffard] cut off his thigh and carried it some distance away.
When we look at the Tapestry, it seems at first as if the artisan leaves us guessing about the identity of the knight who cuts Harold to the ground. But upon closer inspection, we can see that the helmet of the knight points horizontally at the letters TUS:EST (separated out of the words INTERFECTUS EST). There was no reason for the artist to separate these letters from the rest of the words. So then, why did he do so? What is the hidden message? If we reverse the two triplets TUS:EST, we get EST:TUS, which is an abbreviation for EUSTATIUS. The wing of the bird in the upper border and the sword of the man in the next scene both point at the letters.
It cannot be denied that the Tapestry depicts a Norman victory. This was an irrefutable fact. But any contemporary, looking at the Tapestry, could read the story just the way he or she wanted. A Norman supporter, family or ally of William the Conqueror, could interpret the story on the Tapestry from a purely Norman point of view: the throne was promised to William; Harold swore an oath on holy relics, but treacherously was crowned king; William, the rightful heir to the throne, defeated Harold and justly became king of England. An Englishman, supporter, family or ally of Harold Godwinson, or a mere opponent of William the Conqueror, could read the story from another point of view: Harold went to Normandy to discuss the matter of Ælfgyva with William; he swore an oath to confirm the alliance between England and Normandy; on his deathbed, Edward the Confessor designated Harold as his heir; Harold was offered the crown of England by the Witan; William invaded England and Harold was killed.
To the indisputable vagueness of the story on the Tapestry we can add all the elements referring directly or indirectly to Count Eustace II of Boulogne: his ally Guy, count of Ponthieu, the city of Beaurain in the county of Saint-Pol, his prominent role in the Battle of Hastings (he rides beside William of Normandy at a crucial moment, he kills Harold Godwinson, he holds the largest banner), etc., all point in the direction that the Tapestry might have been commissioned by the count of Boulogne. We know that the Tapestry was made in the county of Kent, perhaps at the abbey of St. Augustine’s in Canterbury. This certainly does not contradict the hypothesis that Eustace commissioned the Tapestry, since the 1067 attack on Dover shows that the Kentish people saw him as a valid heir. The Latin words used in the Tapestry point to an author whose mother tongue was French. Was it the designer who was French? Or was the intended audience or recipient French (« French » not necessarily meaning « Norman »)?
The Tapestry was probably designed to decorate a rectangular room in a palace. The earliest known possible reference to the Bayeux Tapestry is to be found in a poem by Baudry of Bourgueil who may have seen (before ca. 1100), somewhere on the Continent, a large tapestry depicting the Conquest of England.
Taking into account the vagueness of the story, the possibility that the Tapestry may have been commissioned by Count Eustace II of Boulogne and the possibility that it was to be seen somewhere on the Continent around 1100, two possible recipients of the Tapestry merit our attention.
The first one is William the Conqueror. Within this scenario Eustace might have commissioned the Tapestry after 1067 (the attack on Dover) and donated it to William as part of his reconciliation process along with the restoration of his English possessions. By having it made in Kent (by his supporters), by showing himself to be a crucial ally of William, by being vague about the « real » story of the Conquest, Eustace managed to conceal his own vindictiveness toward William, presenting William, in fact, with a poisoned chalice. If William the Conqueror was the first recipient of the embroidery, maybe Baudry of Bourgueil saw the Tapestry in one of William’s palaces on one of his many trips through Normandy.
The second possible recipient is Count Eustace II of Boulogne. Within this scenario, Eustace was not only the recipient but also the patron who commissioned the Tapestry. We have seen how Eustace II increased his power and autonomy, turning his county of Boulogne into a powerful and strategic region. Lustre and fame surrounded his name. Eustace II celebrated his noble descent and his family relations with Lorraine, also a family of Carolingian descent, by having it written down. In the course of the 11th century, many great counts and dukes recorded their lineage. Genealogies linking them with Charlemagne provided the princes with an illustrious origin. In those days, prestige could only be gained through an eminent descent, the blood of Charlemagne being the most valuable of all. The oldest genealogia of the counts of Boulogne, written in 1080-1087, not only linked the counts with Charlemagne but also with the celebrated Lorraine dynasty. Eustace was thus very concerned with the lustre of his dynasty. Why not then glorify his military prowess through a captivating embroidery?
If he had commissioned the Tapestry and hung it in the large dining hall of one of his palaces, it would have been a remarkable example of Boulonnais propaganda, showing how important his role had been in the Battle of Hastings and the Conquest of England. His friends and allies could enjoy reading it as a caricature, but at the same time the Tapestry did not contradict the official, Norman, version of events. The Tapestry shows a lot of parallels with the Carmen de Hastingae Proelio and it has been suggested that Bishop Guy of Amiens, a partisan of Eustace and of Count Guy of Ponthieu, wrote the Carmen between 1067 and 1070 to heal the breach between William and Eustace, and to stress French contributions to the Conquest. The Tapestry may have had the same goal. If Eustace had the Tapestry made for his own glory, Baudry of Bourgueil may have seen it in one of Eustace’s palaces in the county of Boulogne.
Brown has argued that the Bayeux Tapestry enjoyed very little circulation and was generally unknown in both England and Normandy. If the Tapestry had been donated by Eustace to William, it probably would have drawn the attention of chroniclers in the king’s entourage. On this basis, it is therefore more plausible that Eustace commissioned it to be exposed in one of his palaces. A remaining question is what happened to the Tapestry between ca. 1100 and 1396. It is true that the embroidery was « an awkward object to exhibit or trundle from one place to another » and that « the amazingly intact condition of the embroidery today attests to the fact that it has not been exposed to handling and exhibition conditions during most of its existence », as Brown and Herrren noted. Eustace died in 1087. If we accept that Baudry de Bourgueil saw the Tapestry on the Continent around 1100, it means that it was still exhibited somewhere on the Continent – maybe the county of Boulogne – around that time. A few years earlier, Eustace’s sons (Eustace III, Godfrey of Bouillon and Baldwin) had responded to the call of the First Crusade. In that case the Tapestry would still have had value, honouring the military prowess of the old count who, just like his sons, fought bravely under the cross. Somewhere between 1100 and 1396, the Tapestry possibly came into the possession of the king of France. This may have happened in 1140 when Eustace IV of Boulogne (1146-1153) married Constance, sister of King Louis VII of France (1137-1180), but we have no sources to confirm this.
Many elements make us assume that the count of Boulogne commissioned the Tapestry as a form of intelligent Boulonnais propaganda. The story, cleverly kept ambiguous, depicted on the Tapestry, can undoubtedly be read in different ways. It can be seen as the official Norman version of what happened in 1066, or as the English interpretation.
Ida of Boulogne
Eustace’s second wife, Ida of Boulogne, was born in Bouillon in around 1035-1040. She was the daughter of the duke of Upper Lorraine and is therefore called Ida of Lorraine or Ida of Verdun. Because of her marriage to Eustace, count of Boulogne, she is also called Ida of Boulogne.
According to her Vita, Ida was beautiful, tall and blond. When after 1056, Eustace II began to administer his territories with the help of household officers who were not kin, Countess Ida kept on playing an important role in the governance of the family’s lands as well. She was probably the moving force behind the reconciliation between her husband and William the Conqueror. She held five manors in England directly from the king: Kingweston (Dorset), Bockhampton, Swanage and Winterbourne Monkton (Somerset) and Nutfield (Surrey). Acting from her landed base around Tongres and her dowry of Genappe, she supported her son Godfrey’s efforts to govern Lorraine in the early 1080’s.
Ida built up a network of ecclesiastical friends. She corresponded with Saint Anselm of Canterbury until her death and she promoted, under his supervision, the Cluniac reform movement. She granted land in Boulogne to the Bec Abbey. The Spanish Bishop Osmond of Astorga sent her, with the permission of King Alphonso VI, some hairs of the Virgin Mary. She suggested to Bishop Drogo and his successor archdeacon Hubert of Thérouanne to establish Saint-Jean au Mont as a dependency of the Norman ducal abbey of Jumièges. She also convinced Hugh of Cluny to send monks to populate her new foundation of Le Wast. Her ecclesiastical patronage was meant to enhance the family’s prestige and strengthen their authority.
She made many donations to religious houses and founded and restored several religious houses: Lens, Saint-Wulmer (Samer), Le Wast, La Capelle (Marck), Boulogne-sur-Mer, etc. She also made many donations to the Abbey of Munsterbilzen, where she was educated. And she was renowned for her donations to the poor.
Ida of Boulogne died on 13 April 1113 in La Capelle. According to her last wishes, her body was brought to the monastery of Le Wast to be buried there.
Mathilda of Boulogne, daughter of Eustace III and wife of Stephen of Blois, urged the Church authorities to canonize her grandmother Ida of Boulogne. The canonization of Ida was part of the campaign to make Stephen king of England. The monks of the Priory of Le Wast, the guardians of Ida’s grave, were asked to write her biography.
The biography can be divided into three parts: (1) her childhood, marriage and motherhood; (2) her life as a widow; (3) miracles and other events that took place at her grave. It is interesting to see how her biographer is in fact reluctant toward the idea of a female married saint. How can a married woman, not a virgin, become a saint? The text places great emphasis on the need for wives to submit to their husbands and on the reproductive function of the female body. Virginity is good, but chastity after childbirth is great. Ida was considered to be a link in a genealogical chain. She married Count Eustace, a hero, of most noble race and of the blood of Charlemagne. Ida was a good Christian wife, pious, obedient and discreet in the management of her home. But most important of all, she was chaste. Her many merits include her giving birth to three sons, among them the king of Jerusalem.
According to her biographer, Ida insisted on breast-feeding her children herself, because she feared that her children might otherwise be exposed to bad influences. We find the same story in the Cycle de la Croisade.
As a saint, she obviously performed miracles. One day, a little girl who was unable to speak took refuge under her cloak. After that, the child began to speak. Her first word was ‘mother’. One day, when Ida was in England, she gave alms to a cripple. As soon as he accepted the gift, he was cured. The sick came to her from far and wide and she cured them through prayers and laying of hands.
After her death, the number of miracles increased. Mathilda, Ida’s granddaughter, was one of the many who were cured.
A few years after her death, Ida’s grave was opened up in the presence of many who had gathered from miles around. Her body appeared to be completely intact, as were her clothes. A pleasant smell arose from the grave: a sign of sainthood.
Cult and relics
As silence fell around the grave, the cult of Saint Ida was reduced to a mere local one. The priory of Le Wast was neglected for ages and in the 16th century, the church being in ruins, a little chapel was built behind the church to shelter the remains of Saint Ida.
In 1669 a priest visited the grave of Saint Ida. The chapel was in lamentable condition. He informed Mère Mectilde du Saint-Sacrement, prioress of the Bénédictines de l’Adoration perpétuelle du Saint-Sacrement in Paris, who was born in Lorraine. She exerted herself to save the relics of her compatriot Saint Ida. With the help of Marguerite de Lorraine (1615-1672), duchess of Orléans, she convinced Bishop François Perrochel of Boulogne (1643-1675) to organise the translation of the relics.
Ida’s grave was opened on the 28th of September 1669, and her bones were transported to Paris. There the duchess of Orléans had two reliquaries made. One of the two, a beautifully sculpted wooden chest, containing most of the remains, was given to the nuns of the Holy Sacrement in the rue Cassette in Paris. After the French Revolution this chest was brought to the Benedictine monastery of Bayeux, where it remains to this day. The other one, made out of ebony and decorated with silver rings, contained a rib of the saint and was sent to the church of Le Wast.
In spite of all the efforts, the worship of Ida of Boulogne was never widely spread. She was mostly remembered as the mother of Godfrey of Bouillon and Baldwin I of Jerusalem. In the Old French Cycle de la Croisade, she appears as the daughter of the Swan Knight (Le Chevalier au Cygne), who married the count of Boulogne. It was especially her son Godfrey of Bouillon, a hero of the First Crusade, who appealed to the imagination. The chronicler Guibert of Nogent tells us that Ida herself told heroic stories about her son Godfrey: The glorious woman used to say, when she marvelled at the result of the journey and the success of her sons, that she had heard from the mouth of her son the duke a prediction of the outcome long before the beginning of the expedition. For he said that he wanted to go to Jerusalem not as a simple pilgrim, as others had done, but forcefully, with a large army, if he could raise one.
 R. D’Amat, « Eustache, comte de Boulogne », in Dictionnaire de Biographie Française, 13, col. 271-272 ; J.C. Andressohn, The Ancestry and Life of Godfrey of Bouillon, Bloomington, 1947, p. 20-25 ; H. van Cuyck, The Count and the Saint. Eustace and Ida of Boulogne, Oostkamp, 2013 ; H.J. Tanner, « Eustace (II), Count of Boulogne (d. c. 1087) », in Oxford Dictionary of National Biography, Oxford, 2004.
 A detailed analysis can be found in: H. van Cuyck & V. Lambert, ‘Count Eustace II of Boulogne (1047-1087) and the Bayeux Tapestry: a reappraisal of the evidence’, in: Annales de Normandie, 64/2 (2014), pp. 137-167.
 About Ida, Eustace’s second wife, see: J.C. Andressohn, The Ancestry and Life of Godfrey of Bouillon, Bloomington, 1947. R. Aubert, ‘Ide de Boulogne’, dans: Dictionnaire d’Histoire et de Géographie Ecclésiastiques, 25, Paris, 1995, col. 644-646. J. Coenen, Een onbekende Limburgse heilige: Ida van Boolen, Maaseik, 1952. H. van Cuyck, Le Comte et la Sainte. Eustache et Ide de Boulogne, Oostkamp, 2013. H. van Cuyck & V. Lambert, ‘Ide de Lorraine, mère de Godefroid de Bouillon’, in: Bulletin du Cercle historique de Bouillon, 16 (2013), pp. 54-57. H. van Cuyck & V. Lambert, ‘Ida van Lotharingen, ook Ida van Boulogne of Ida van de Ardennen, gravin van Boulogne, heilige’, dans : Nationaal Biografisch Woordenboek, vol. 21, col. 523-530 (Bruxelles, Koninklijke Academiën van België, 2014). J.P. Dickès, Sainte Ide de Boulogne, Paris, 2004. F. Dieckmann, Die Lothringischen Ahnen Gottfrieds von Bouillon, Kisling, 1904. F. Ducatel, Vie de Sainte Ide de Lorraine, comtesse de Boulogne, Boulogne, 1900. N. Huyghebaert, ‘La mère de Godefroid de Bouillon, la comtesse Ide de Boulogne’, dans : Publications de la section historique de l'Institut Grand-Ducal de Luxembourg, 95 (1981), pp. 43-63. H. Platelle, ‘Ide, comtesse de Boulogne’, dans: Nouvelle Biographie Nationale, II, Bruxelles, 1990, pp. 233-234. A. Le Roy, ‘Ida’, dans : Biographie Nationale, X, Bruxelles, 1888-1889, col. 3-4. H. J. Tanner, Families, friends, and allies: Boulogne and politics in northern France and England, c. 879-1160, Leiden, 2004.
 Acta Sanctorum, April. II, pp. 141-145 (3rd ed. pp. 141-146).
 A detailed history of the relics of Saint Ida can be found in: H. van Cuyck & V. Lambert, ‘Les reliques de Sainte Ide, mère de Godefroid de Bouillon’, in: Bulletin de la Société des antiquaires de Normandie, 73 (2014), at press. See also: H. van Cuyck & V. Lambert, Een reliek van de H. Ida, moeder van Godfried van Bouillon, in Walchsee (Oostenrijk), academia.edu, 2014. Click here to see a presentation about the relics (in French).