Premiership of David Cameron

Premiership of David Cameron began on 11 May 2010 when Cameron accepted the Queen's invitation to form a government. This occurred upon the resignation of Cameron's predecessor as Prime Minister of the United Kingdom, Gordon Brown. While serving as prime minister, Cameron also serves as the First Lord of the Treasury, the Minister for the Civil Service and the Leader of the Conservative Party. Cameron is prime minister at the head of a coalition government between the Conservative Party and the Liberal Democrats following the 2010 General Election in which no party gained an overall majority in the House of Commons.
At the 2010 general election on 6 May, the Conservative Party achieved its highest number of seats since the 1992 election, returning 306 MPs. However, it was still 20 seats short of an overall majority, resulting in the nation's first hung parliament since February 1974.
Talks between Cameron and Liberal Democrat leader Nick Clegg led to a coalition of the two parties, enabling Her Majesty The Queento invite Cameron to form a government.

First day in office
Cameron and his wife Samantha Cameron were driven from Buckingham Palace arriving at Downing Street at about 20:55 on 11 May 2010. Cameron made a speech which started with a short tribute to the out-going Prime Minister, Gordon Brown, and the former Labour government.He went on to describe the "difficult decisions" to reach "better times ahead". Cameron and his wife entered 10 Downing Street together. He soon received a telephone call from United States President Barack Obama, the first foreign leader to congratulate him on his premiership.
Cameron met with his MPs in the Committee Room of the Commons at 22:00 on 11 May, celebrating, with cheering audible from the central hall of the Commons. It is likely that he then explained the details of any coalition agreements made between the Conservatives and the Liberal Democrats to his MPs.

Full wikipedia article