[3] At Easter 1138, he accompanied his half-brother Waleran de Beaumont, 1st Earl of Worcester on an embassy to Paris for the purpose of ratifying a treaty between the English and French kings.

[6] On 2 February 1141, he and his half-brother Waleran were again with King Stephen at the Battle of Lincoln but fled at the initial charge of the enemy forces.

[5] They both joined Queen Matilda but on King Stephen's release they were once again among his followers, and William witnessed a royal charter at Canterbury in late 1141.

They were joined by remnants of the army of the Holy Roman Empire, which had previously suffered heavy losses at the Battle of Dorylaeum in 1147.

They marched across southwest Turkey and fought an unsuccessful battle at Laodicea (3–4 January 1148) on the border between the Byzantine Empire and the Sultanate of Rum.

On 6 January 1148, they battled again in the area of Mount Cadmus, where Turks ambushed the infantry and non-combatants only, because they had become separated from the rest of the army.