Simon Islip was an English prelate

Prelate

A prelate is a high-ranking member of the clergy who is an ordinary or who ranks in precedence with ordinaries. The word derives from the Latin prælatus, the past participle of præferre, which means "carry before", "be set above or over" or "prefer"; hence, a prelate is one set over others.-Related...

. He served as Archbishop of Canterbury

Archbishop of Canterbury

The Archbishop of Canterbury is the senior bishop and principal leader of the Church of England, the symbolic head of the worldwide Anglican Communion, and the diocesan bishop of the Diocese of Canterbury. In his role as head of the Anglican Communion, the archbishop leads the third largest group...

 between 1349 and 1366.

Lord Privy Seal

In 1347, possibly in September, Simon was appointed keeper of the Privy Seal. Previously he had held the seal of Lionel, who was the regent in England. He vacated the office between 21 February and 1 May 1350.

Archbishop of Canterbury

Simon was elected to the see of Canterbury on 20 September 1349, provided to the see on 7 October 1349, and entrusted with the temporalities of the diocese on 15 November 1349. His consecration took place on 20 December 1349.