Sorry I didn't notice your post earlier. I would be happy to add my two-cents-worth.

The Carmen de Hastingae Proelio is my favorite original source. (It too prickled at my short hairs when I first read it: "where has THIS been all of my life?" I asked aloud as I read the part where William unhorses the Manceaux knight and mounts up in his place.)

And Morillo's book is my favorite seminal source. He did include ALL the original sources. By "original", we should understand them to be all demonstrably contemporary sources to the battle of Hastings, as compared with later "seminal" works based on the originals, e.g. Malmesbury, Huntington, Wace.

The Bayeux Tapestry almost without doubt was produced before the exile of Odo (c. 1083, iirc); and I lean toward a very early date before 1070; even as early as the spring of 1067. Similarly, the content and immediate detail of the Carmen, and its evident author (bishop Guy of Amiens, a Ponthievin, and uncle to the count of Ponthieu, the Guy who captured Harold Godwinson in 1064 and delivered him up to duke William)) makes for a very early dating of it, c. the same time as the Bayeux Tapestry.

Internal evidence indicates that one influenced the other, but it is impossible to tell which came first: my personal favorite theory is that the Carmen was written and performed before the Tapestry was completed or even begun, and that the Carmen was held forth as an *authority* of what happened until it was discredited by William of Poitiers' later-Gesta Willelmi.

It is obvious from a comparison of the Carmen and the Gesta, that the Gesta borrowed from the Carmen and not the other way around; and the Gesta was composed sometime in the mid to late 1070's, most likely before count Eustace of Boulogne was reinstated to royal favor.

(He had been out since the fall of 1067, over his rebellion against William, and his and Kent's attempt to place Eustace's grandson, iirc, on the throne of England.)

The reason why the Carmen became unpopular seems self evident: the account of Harold's death, involving duke William as one who cut him to bits, was threatening his reign by 1069-70, when rebellions in England arose in the north. William could no longer allow Harold's memory to be tinged with hero worship. He quashed any references to Harold's having even once been legitimate king of England. The Tapestry consistently refers to Harold as "king". But by the time of the Domesday Book (1086) Harold is only called "earl" and never "king" Harold.

The Carmen's account of Harold's death had become embarrassing to William and his need for a strong anti-Harold propaganda. By the rebellions period, the Tapestry (assumedly) had already done its work in that regard: I envision the Tapestry as having been put on display as a sort of traveling media show, in the various church naves around the realm, to inform the populace of the official reason why the Norman conquest had to take place.

But the situation with the Carmen was different. It said pointed things about William's involvement with Harold's demise which could not be helpful. Further, it held forth a rather disparaging point of view as regarding the Norman prowess at the battle of Hastings, and gave greater glory to the French contingent (a natural prejudice for a Frenchman such as the bishop of Amiens), and it painted count Eustace in a heroic light only second to duke William himself. The fact that William of Poitiers' Gesta became the primary source for the battle later, indicates a complete rewriting of the official version of history to suit the ducal and royal interests; most likely under king William's direct command that such a history be composed in the first place.

But the reason why some modern scholars do not like to believe in the Carmen is based almost entirely on what they perceive as anachronisms: the fact that a Roland chanson is sung by one Taillefer is their biggest beef, because they have this conceit that the Roland saga wasn't first introduced in a chason until the 12th century at the royal French court; and neither is Taillefer mentioned in any early source, but only by name in 12th century sources: ergo, the Carmen must be a 12th century product.

But the internal evidence is strongly against this dating. Taillefer does not perform in the Carmen as he does in the later sources: he has a "job", to bolster the courage of the Franco-Norman army. And there is no augmentation of his role, he kills his man (singular), takes his head and returns to the obscurity of the Norman ranks never to be mentioned again: in the later sources, he kills two or several Englishmen and then dies gloriously, deeply imbedded in the English ranks. As for the Roland saga's dating, the legendary material was certainly well known long before the song of Roland was composed in the 12th century. It is known that there was a mid-11th century version of the Chanson de Roland composed by a French trouvère, which became the main inspiration of an Anglo-Norman scribe's late-12th century version; so the objection that there couldn't be a Taillefer singing of Roland before the battle of Hastings has no foundation.

R. Allen Brown objected to the Carmen on the basis of its account being too detailed and unbelievable: if William had in fact participated in the death of Harold with only three compaions attacking his command post, such a feat would have been "bruited about the courts of Europe." But we hear nothing about it outside the Carmen's sole account.

However, I brush this aside by noticing that medieval accounts of named commanders in battle tend toward making them out as alone, when in fact they are at the head of a body of troops: instead of reading the Carmen as only William, Eustace, Gilfardus and the "noble heir of Ponthieu" (Hugh, most likely the brother of count Guy of Ponthieu), we should instead envision each as the commander of his own conroi of mounted knights: a conroi could be anywhere from 20 to 50 men in size, so William and his three companions were not suicidally attacking Harold's core of his army alone. As for such a feat being "bruited about the courts of Europe": first of all, we would have to accept that William welcomed the notoriety, and apparently he did not. Secondly, we have to accept that the story was true in the first place, and it probably is not, but was meant only as an acceptable exaggeration to pump William's ego up (the work of any competent trouvère, if he wants to be well paid). I personally do not doubt the basic story, that William's troops in the final attack dismembered Harold; whether or not William actually had a personal hand in it is immaterial.

The Carmen was not trying to be a historically accurate documentation of the battle of Hastings. (Such documentation was not conceived at the time.) It was trying to impress William, to gain his favor: possibly to speak well for bishop Guy with the pope (Guy was not enjoying the exercise of his bishopric, because of some legal troubles then unresolved, and possibly wanted the new king's help and influence, and gave him a gift of his "song of the battle of Hastings" to that end); or to help Eustace of Boulogne get back into favor with William. Anyway, it missed its mark and fell out of favor instead; possibly it was officialy supressed.

Morillo's book, btw, came out before Frank Barlow's edition of the Carmen in 1999. Barlow has largely found that Morton and Muntz were right in claiming that the Carmen is a source composed very soon after the battle of Hastings. I think the detractors have a lot of work to do to overturn Barlow's position. Personally, I believe the Carmen is really an early work and not some 12th century product. The evidences for the latter position are far less convincing, from what I have read and seen quoted.

As Barlow says in his lengthy introduction (over half the volume): "When all the points raised in this controversy are considered, it seems fair to say that, although it cannot be proved that the anonymous poem is Guy's, the attribution cannot be disproved. Moreover, the weight of the evidence is in favour of the poem having been used by William of Poitiers. If that is accepted, it is otiose to prevaricate further."