Conservative leader David Cameron was appointed prime minister by the Queen tonight after holding his first private audience with her.
He arrived with his wife Samantha at Buckingham Palace less than half an hour after Mr Brown had left.
Mr Cameron is the 12th prime minister of the Queen's reign and following tradition "kissed hands" - in reality shaking hands - after accepting her offer to form a new government.
Buckingham Palace released a statement following the audience, which lasted almost 25 minutes.
It said: "The Queen received the Right Honourable David Cameron this evening and requested him to form a new administration.
"The Right Honourable David Cameron accepted Her Majesty's offer and kissed hands upon his appointment as Prime Minister and First Lord of the Treasury."