Andy Burnham officially became British Prime Minister on Monday following a meeting with King Charles III, making him the seventh prime minister of Britain in a decade. 

Burnham, the former mayor of Greater Manchester, replaces outgoing Prime Minister Keir Starmer, who announced his resignation outside the prime minister's official residence at 10 Downing Street in London on Monday morning, ABC News reported. 

Burnham was officially declared head of Britain's governing Labour Party on Friday, which cleared a final hurdle before the meeting with King Charles. 

Starmer announced in June that he'd step down, which followed months of domestic political turmoil.