William de Cantilupe, 1st Baron Cantilupe

William's father died when he was aged four and was buried in St Mary's Church, Ilkeston where survives his recumbent effigy and chest tomb, showing him as a "lively" cross-legged warrior, often said to be a depiction reserved for crusaders.

The senior line died out in the male line in 1273 on the death of his first cousin, 22 year-old Sir George de Cantilupe (1251-1273), 4th feudal baron of Eaton Bray, Lord of Abergavenny, who had inherited vast Welsh estates from his mother Eva de Briouze.

In May 1274 at the age of 12 he accompanied his uncle Thomas de Cantilupe, who would be appointed Bishop of Hereford the following year, to the Second Council of Lyons.

He was present at the Siege of Caerlaverock Castle in Scotland in 1300, when his armorials, a version of the arms of the senior line differenced by a fess vair (as seen on his surviving 1301 seal), were blazoned in Norman-French verse in the Caerlaverock Roll as follows: Translated by Sir Nicholas Harris Nicolas as: "And William de Cantilupe, whom I for this reason praise, that he has at all times lived in honour.

It has been suggested[19] that the (heavily restored) recumbent stone effigy of a knight in Felixkirk Church, near Ravensthorpe, is his monument, although others believe it to represent John de Walkyngham (d.1284)[20]