Conservative leader David Cameron has become the new UK prime minister after the resignation of Gordon Brown.
Mr Cameron, 43, entered 10 Downing Street after travelling to Buckingham Palace to formally accept the Queen's request to form the next government.
He said he aimed to form a "proper and full coalition" with the Liberal Democrats to provide "strong, stable government".
His party won the most seats in the general election last week, but not an overall majority.
In a speech outside his new Downing Street home, Mr Cameron said he and Liberal Democrat leader Nick Clegg would "put aside party differences and work hard for the common good and the national interest".
David Cameron paid tribute to outgoing Prime Minister Gordon Brown for his long years of public service and pledged to tackle Britain's "pressing problems" - the deficit, social problems and to "rebuild trust in our political system".
Mr Cameron's arrival in Downing Street marks the end of 13 years of Labour rule and sees the first coalition government in the UK in 70 years.
It is also the first Liberal Democrat and Conservative power-sharing deal at Westminster in history.
Mr Cameron is the youngest prime minister since 1812 - six months younger than Tony Blair when he entered Downing Street in 1997 - and the first Old Etonian to hold the office since the early 1960s.
US President Barack Obama was the first foreign leader to congratulate Mr Cameron in a brief telephone call.
Mr Cameron has begun the work of appointing his first cabinet - with George Osborne confirmed as chancellor and William Hague as foreign secretary.
There are expected to be top jobs for Liberal Democrats in the new coalition, with speculation that their party leader, Nick Clegg, will be the deputy prime minister.
In his speech on the steps of Downing Street, Mr Cameron eschewed the high flown rhetoric or even poetry favoured by some of his predecessors.
Instead he stressed there would be "difficult decisions" but said he wanted to take people through them to reach "better times ahead".
He said he aimed to "help build a more responsible society here in Britain... Those who can should and those who can't, we will always help. I want to make sure that my government always looks after the elderly, the frail, the poorest in our country.
"We must take everyone through with us on some of the difficult decisions we have ahead.
"I came into politics because I love this country, I think it's best days still lie ahead and I believe deeply in public service.
"I think the service our country needs right now is to face up to our big challenges, to confront our problems, take difficult decisions, lead people through those decisions, so that together we can reach better times ahead."
Here at Greengates Builders Merchants Accrington, Lancashire we are hoping that with a new Prime Minister now in place our country can move forwards!