(that is, the son and heir of Philip III).^25 Whatever the truth on this point,
it was the magnitude of Beatrice’s lineage and contacts that really
attracted attention. The wedding marks thefirst formal alliance between
the Châtillons, the Champenois dynasty that had done best within
France itself (not least, through rising to become counts of Blois), and
the Briennes, the standout family further afield.^26
The marriage produced a son and heir, the future John III, and, it
seems, several daughters.^27 Although most of these would go on, in their
turn, to wed significant Frenchfigures, the match that really stands out is
that of Matilda (or Mahaut), since it has been intriguingly suggested that
she married Alfonso de la Cerda. Alfonso and his younger brother,
Fernando, were the sole descendants, in the senior line, of their grand-
father, King Alfonso X of Castile. However, on the death of the boys’
father in 1275, their uncle, the Infante Sancho, was recognized as the
rightful heir. The French crown was deeply involved in this: above all,
because the de la Cerdas were the sons of Philip III’s sister, Blanche.
King Philip promptly dispatched John of Brienne, the former count of
Montfort and butler of France, to try to protect the rights of his kinsmen.
In the event, we are told, John was badly treated, and he was fortunate to
return home in one piece, bearing the French king’s widowed sister.^28 It
is not surprising, then, that a short, sharp war broke out in 1276, which
ground to a halt in the Pyrenees.^29 This was, in fact, just one of several
unfortunate Iberian entanglements that collectively soured Philip’s reign,
and they culminated, of course, in his abortive crusade against Aragon in
1284 – 5, in the course of which the king died. By then, of course, Sancho
had succeeded to the Castilian throne. Indeed, to all intents and pur-
poses, he had thrown his own father off it. It is tempting to follow David
Masnata in suggesting that, at around this juncture, Alfonso de la Cerda
was desperate to assure himself of French backing, and it did look like it
would be forthcoming. A team of negotiators acting for the new French
king, Philip IV, played a highly significant role in pushing Sancho to offer
quite remarkably good terms to the de la Cerdas in July 1288–and
amongst these negotiators, once again, was John, the butler of France.
(^25) Chronique des comtes d’Eu, 444.
(^26) For an overview of the rise of the house of Châtillon, see Evergates,Aristocracy, 176–8.
(^27) For example, theChronique des comtes d’Eusuggests that John II had two daughters, and
names them as Isabella and Margaret (444). For doubts about whether the latter was
indeed John’s daughter, see P. Marchegay,Recherches historiques sur le département de la
Vendée (ancien Bas-Poitou) (La Roche-sur-Yon, 1859), 224.
(^28) See the account inChronographia regum Francorum, ed. H. Moranvillé, 3 vols. (Paris,
291891 – 7), i, 7–8.
The best account of this conflict is still to be found in C.-V. Langlois,Le règne de Philippe
III le Hardi(Paris, 1887), 104–7.
The House of Eu and Guînes 109