Then mayor of Greater Manchester Andy Burnham (left) and Mayor of Liverpool City Region Steve RotheramA written constitution could be needed for Britain as a “different approach” is taken to running the country, the Prime Minister has said. Andy Burnham previously called for a written constitution in 2024 book Head North: A Rallying Cry For A More Equal Britain, which he co-authored with Liverpool City Region metro mayor Steve Rotheram. The reinstalled original Magna Carta inside the medieval Chapter House at Salisbury Cathedral (Ben Birchall/PA)The former mayor of Greater Manchester said he thought that approach should be the “cornerstone” of a written constitution. “That does start to take you into the realms of a very different approach to running the country.” Unlike many countries, the UK does not have a formal written constitution document, but it is understood to have a constitution established through history by common law, statutes and conventions.