Cameron rides into Number 10 after 24 hours on rollercoaster

Four days later than he had hoped to be entering the prestigious address, Mr Cameron became the first Conservative Prime Minister in 13 years and the youngest since 1812.

With a sombre face - in stark contrast to the fanfare and glitz of Tony Blair's arrival 13 years ago - Mr Cameron helped pregnant wife Samantha out of the car before addressing the nation for the first time in front of his new home.

"Her Majesty the Queen has asked me to form a new Government and I have accepted," he said before paying tribute to his predecessor, outlining the problems ahead, demanding more responsibility and warning the work would be "hard and difficult".

His address complete, he turned and trod the few yards to turn and pose in front of the black door with Samantha looking less than comfortable in the glare of the world's media but smiling nonetheless.

Just 90 minutes earlier Gordon Brown had emerged from that door to announce he would tender his resignation to the Queen, bringing to an end days of wrangling following the election ending in a hung parliament.

After saying an emotional farewell to staff gathered in a horseshoe behind the front door, Mr Brown strode to the same podium where the previous day he had offered up his career in a last-ditch bid to keep Labour in power. In the end, it was to no avail.

His voice cracking with emotion and with wife Sarah at his side, Mr Brown said it had been a "privilege to serve". A crowd watched through the gates of Downing Street but although they could not hear his words there was still a hush.

After signing off with the words "Thank you, and goodbye", he entered Number Ten for the final time, collected sons John and Fraser - normally sheltered from the public glare - and made his final journey as Prime Minister, travelling to Buckingham Palace to see the Queen.

With the trappings of office gone - the motorcycle outriders accompanying him to the Palace were nowhere to be seen on his exit - he headed to his spiritual home, not the road where he has lived for 13 years as Chancellor and Premier but the central London headquarters of the Labour party.

Among party friends, he was met with applause and warm hugs before delivering an impassioned speech extolling pride in Labour's record in power as he declared: "I'm Labour and Labour I will always be".

It brought to a close an historic day during which MPs and journalists alike had been gathering longing for news of the wranglings over who would govern the country.

In Portcullis House, the parliamentary office block opposite the Palace of Westminster, new MPs had been more focused on their induction itineraries and played with their newly issued Blackberries or laptops but veterans were more interested in the gossip and intrigue.

Through the morning there was little news to chew on - negotiations between Labour and the Liberal Democrats came and went, but it was not until mid afternoon that it became apparent those talks had actually broken down.

Liberal Democrat MPs, faced with a decision which has tested many of their core beliefs, slowly convinced themselves there really was no other option but to strike a deal with the Tories. In the end, head - that only this deal could offer stability and strong government - had to rule heart, which insisted that they were ideologically closer to Labour.

Suddenly there was a buzz around Westminster, a sense of anticipation. Rolling news cameras focused on the black door of Number Ten, Labour Ministers admitted the game was up and a media pack waited outside the Cabinet Office where the Tories and Liberal Democrats negotiations were nearing a conclusion.

All we needed was confirmation the Labour government was over. But as Number Ten officials donned their suits in place of casual dress for the occasion, the Prime Minister was cracking jokes with staff in a final act of gallows humour.

At 7.07pm the podium - scene of Mr Brown's dramatic resignation announcement the previous day - was erected in the middle of Downing Street and soon afterwards the painfully slow demise of a Prime Minister was complete.