A native of Perth and a fisherman by trade, he experienced a conversion as a young man and devoted himself to the care of orphans and the poor, once saving from certain death an infant left at the door of the church. In accordance with a vow, he set off on pilgrimage to the Holy Land in 1201.
He took with him but one companion, a young man, who, after they reached Rochester, diverted him on a supposed short-cut and murdered him for his few possessions. His body was found by a madwoman, who garlanded it with honeysuckle and was cured of her madness through it. Other miracles were soon claimed. William was buried in Rochester cathedral, first in the crypt and then in the north-east transept, where offerings at his shrine contributed towards the rebuilding work of the cathedral.
In 1256 Laurence, bishop of Rochester, seems to have obtained some kind of papal approval of the cult. Recorded offerings at the shrine by King Edward I (1300) and Queen Philippa (1352) attest royal interest, while bequests of the 15th and 16th centuries are evidence for its continued local popularity.
St William's hospital, on the road to Maidstone, marks the place of his death. Feast: (according to C.S.P.), 22 April; other authorities give 23 May.
AA.SS. Maii V (1685), 268–9; N.L.A., ii. 457–9; W. H. St John Hope, The Cathedral Church and Monastery of St Andrew at Rochester (1900).