As an alderman, Blackaller had law enforcement responsibilities, occasioning active measures, and he was involved in the putting down of an open riot against the dissolution of St Nicholas' Priory in 1536, where he was driven from the church.
[3] In 1537, Blackaller expropriated land at Shillingford which had been granted to the Dean and Chapter of Exeter Cathedral, refusing to pass rents on to the clerics.
Uprisings at Sampford Courtenay and Clyst St Mary escalated, with rebels building defensive works and blocking highways.
[7] 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.
[3][8] Whilst Blackaller had sympathy with the cause, his dedication to the King and his duty were stronger than his religious conviction,[9] for which later commentators have characterised him as heroic and courageous.