During Blackaller's final term as Mayor of Exeter in 1549, the
Prayer Book Rebellion took place following the release of the
first Book of Common Prayer and related religious changes under
Edward VI, suppressing the practice of Catholicism. Uprisings at
Sampford Courtenay and
Clyst St Mary escalated, with rebels building defensive works and blocking highways. Devon
Knight and
Privy Councillor
Peter Carew was tasked with quelling the uprising, but was unsuccessful, but did alert Blackaller to the danger, allowing Exeter to be brought to a state of defensive readiness. The
midsummer eve celebrations were cancelled, which would normally have involved a ceremonial inspection of the city's defences, followed by a feast. Whilst Blackaller had sympathy with the cause, his dedication to the King and his duty were stronger than his religious conviction, for which later commentators have characterised him as heroic and courageous. An initial force of around 2,000 rebel men gathered outside Exeter's city gates, initiating a five-week long siege. ==References==