Andy Burnham is set to become Britain's first openly Catholic prime minister, taking office as Sir Keir Starmer prepares to deliver his farewell speech from Downing Street. The milestone is significant because, until relatively recently, safeguards existed to separate the role of Downing Street from the monarch's constitutional position as Supreme Governor of the Church of England, meaning a Catholic PM's faith does not affect the Crown's religious duties.

Burnham becomes the UK's seventh prime minister in a decade, with markets watching closely to see whether Ed Miliband is given the role of Chancellor at Number 11. The change comes nearly 500 years after the English Reformation first raised questions about the relationship between the monarchy, the Church of England and the country's political leadership.