Bullock was a canon regular in the diocese of St. Andrews, and on 23 March 1409, is recorded as holding the vicarage of Dull in the diocese of Dunkeld when Avignon Pope Benedict XIII granted his petition to hold the vicarage of Tranent in the diocese of St Andrews [REF].
A letter of Benedict XIII, dated 5 June 1417, reveals that John Bullock was one of three clergymen claiming the title Prior of St Andrews, a claim which he seems to have given up in the following year when he had the chance to become Bishop of Ross [REF].