"Let the work of change begin," Gordon Brown declared today as he returned to Downing Street as the new prime minister of Great Britain.
A beaming and emotional premier pledged to use "all the talents" as he prepared to reshape the cabinet and government.
Speaking with his wife, Sarah, beside him, Mr Brown told reporters: "I have just accepted the invitation of Her Majesty the Queen to form a government.
"This will be a new government with new priorities and I have been privileged to have been granted the great opportunity to serve my country."
He promised to be at all times "strong and steadfast" and to govern beyond narrow political interests.
Mr Brown said: "The need for change cannot be met by old politics," as he pledged to build a government that would use all the talents "in the spirit of public service that will make our nation what it can be".
"At all times I will be strong in purpose, steadfast in will, resolute in action in the service of what matters to the British people, meeting the concerns and aspirations of our whole country," he said.
The 56-year-old Scot, who took over as Labour leader on Sunday, spent almost an hour with the Queen before emerging from Buckingham palace as prime minister, first lord of the Treasury and minister for the civil service.
Outside No 10 Mr Brown said that he represented the town where he grew up and went to school.
"I wouldn't be standing here without the opportunities that I received there. I want the best of chances for everyone. That is my mission," he said.
"If we can fulfil the potential and realise the talents of all our people then I am absolutely sure that Britain can be the great global success story of this century."
Tributes flowed in to the new prime minister this afternoon.
George Bush called Mr Brown to offer his congratulations, while Scotland's first minister and fellow Scot Alex Salmond wished the new prime minister success by letter.
Mr Salmond wrote: "You will bring many outstanding personal qualities to the job, and I have no doubt that you will give of your best.
"I look forward to working closely with you in the best interests of Scotland, and, to that end, would very much welcome the opportunity for an early meeting."
The mayor of London, Ken Livingstone, said he was looking forward to working with Mr Brown, as he set out the future relationship he hopes to have with the new prime minister.
The two men have had their share of fallouts, most notably over the government's decision to introduce part-privatisation of the tube, which was pushed through by Mr Brown as chancellor.
But Mr Livingstone said: "As chancellor Gordon Brown played a decisive role in restarting public investment in London after decades of neglect.
"Without the investment we have seen, London would not be able to sustain the huge success it is currently enjoying, and I am sure that as prime minister Gordon Brown will develop this further.
"I particularly look forward to working with Gordon Brown and his government on the key projects for London of the Olympics, more affordable housing and Crossrail."