In the 2011 census, 59.4% of the population of England specified their religion as Christian, 24.7% answered that they had no religion, 5% specified that they were Muslim, while 3.7% of the population belongs to other religions and 7.2% did not give an answer. Christianity is the most widely practised religion in England, as it has been since the Early Middle Ages, although it was first introduced much earlier in Gaelic and Roman times. This Celtic Church was gradually joined to the Catholic hierarchy following the 6th-century Gregorian mission to Kent led by St Augustine. The established church of England is the Church of England, which left communion with Rome in the 1530s when Henry VIII was unable to annul his marriage to the aunt of the king of Spain. The church regards itself as both Catholic and Protestant.