During the medieval period, Kent produced several rebellions including the Peasants' Revolt led by Wat Tyler and later, Jack Cade's rebellion of 1450. Thomas Wyatt led an army into London from Kent in 1553, against Mary I. Canterbury became a great pilgrimage site following the martyrdom of Thomas Becket, who was eventually canonised in 1246. Canterbury's religious role also gave rise to Chaucer's "Canterbury Tales", a key development in the rise of the written English language and ostensibly set in the countryside of Kent. Rochester had its own martyr, William of Perth, and in 1256 Lawrence, Bishop of Rochester travelled to Rome to obtain William's canonisation.