Tory leader David Cameron has entered Number 10 Downing Street as Prime Minister for the first time - and said: "This is going to be hard and difficult work."
He told the waiting media:"On behalf of the whole country I would like to pay tribute to the outgoing Prime Minister for his long record of dedicated public service."
And he added: "I aim to form a proper and full coalition between the Conservatives and the Liberal Democrats.
"Coalition will throw up all sorts of difficulties but I believe that together we can provide that strong and stable government that our country needs."
US President Barack Obama has congratulated him by telephone and Downing Street staff showed Mr Cameron's pregnant wife Samantha around Number 10.
The couple arrived there straight from Buckingham Palace where the Tory leader had accepted the Queen's request for him to form a new government.
David Cameron meets the Queen as Gordon Brown quits as Prime Minister
Mr Cameron accepts the job, offered by the Queen
And as his silver Jaguar entered the security gates to Downing Street, he was greeted by a mixture of cheers and jeers from crowds gathered on Millbank.
Sky News' royal commentator Alastair Bruce said the Queen would have asked the Tory leader the constitutional question "Will you form the new administration?" and the moment he said "Yes" he became prime minister of the UK.
Mr Bruce added: "And then his wife would have been invited into the room and they would all have had a jolly good chat."
Mr Cameron is the 14th prime minister the Queen has dealt with.
Sky News' royal correspondent Sarah Hughes said Mr Cameron's audience with the Her Majesty lasted some 25 minutes.
