The group of coins in the names of William" and "Henry" and struck at the Angevin mints, particularly Hereford and Gloucester, are attributable, at least in part, to Earl William FitzRobert of Gloucester and Henry of Anjou (the future Henry II). William FitzRobert was the son of Robert, 1st Earl of Gloucester, an illegitimate son of King Henry I of England, during whose reign William was born. Thus William was a nephew of the Empress Maud and a cousin of King Stephen, the principal combatants of the English Anarchy period. It also meant that William is the great-grandson of William the Conqueror.
BNS Research Blog article by Alex Bliss on some of the coins of Henry of Anjou