Brown is PM after 13-year wait

Speaking outside No 10 after being invited to form an administration by the Queen during an audience lasting almost an hour, he said he would live up to his old school motto: "I will try my utmost."

Mr Brown promised to reach out beyond narrow party politics and form a Government that "uses all the talents".

He is putting the final touches to his Cabinet, which will be announced at lunchtime on Thursday. The Prime Minister's spokesman refused to comment on reports that Foreign Secretary Margaret Beckett and Health Secretary Patricia Hewitt would be first for the axe - though neither move would surprise Westminster.

Mr Brown's final act as Chancellor was to appoint his predecessor Tony Blair to the office of stewardship of the Chiltern Hundreds - meaning the ex-premier will stand down as MP for Sedgefield.

Mr Blair bowed out of British politics after being appointed an envoy to the Quartet group - the United States, United Nations, the EU and Russia - seeking to broker peace in the Middle East. He brandished his P45 at Question Time in the Commons and effectively left parliament with the words: "That is that. The end."

After saying his goodbyes to No 10 staff, Mr Blair left Downing Street for the last time to tender his resignation to the Queen at Buckingham Palace. But first, he appeared on the steps of No 10 with his wife, Cherie, sons, Euan, Nicky and Leo, and daughter, Kathryn, for a final family photograph in front of the press.

As his children went back into the house, Mr and Mrs Blair got into his prime ministerial Jaguar to take the short trip to Buckingham Palace, travelling up Whitehall and along the Mall. Stepping into the car, Mrs Blair - who has had a difficult relationship with the media over the last decade - told reporters and photographers: "Bye, I don't think we'll miss you."

Minutes later, Mr Blair was ushered into Buckingham Palace via the King's Door for his final audience with the Queen as premier. As Mr Brown left the Treasury with his wife, Sarah, to head for Buckingham Palace, he was cheered on by staff and long-time political allies.

On returning to Downing Street as Prime Minister, he told reporters: "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."