Britain on Tuesday ushered in a new political era, with new Prime Minister David Cameron leading the first ruling coalition in decades.

Five days after the general election, Cameron's Conservatives sealed a coalition deal with Nick Clegg's Liberal Democrats, the third largest party in the British political realm, which became the kingmaker due to the inconclusive result of Thursday's vote.

The alliance marks an historic moment in Britain's political history, as it is the first time since Winston Churchill's wartime government during the Second World War that the country has a coalition government and that the Liberal Democrats are part of the government. It is also the first time that the Conservatives and the Liberal Democrats join hands in governing the country.

Meanwhile, the 43-year-old new leader is the youngest British prime minister for nearly 200 years, and is also the 12th prime minister under the Queen's reign. He is also the first prime minister in over 40 years who was educated at the prestigious school, the Eton College, which now boasts 19 British prime ministers, out of a total of 53.

Queen Elizabeth II invited Cameron to the Buckingham Palace and confirmed him as prime minister, shortly after his predecessor Gordon Brown announced his immediate resignation as prime minister and Labour party leader in the early evening.

Speaking at No. 10 Downing Street, the official prime ministerial office and residence, Cameron noted that his country is faced with "some deep and pressing problems -- a huge deficit, deep social problems, a political system in need of reform. "

"For those reasons, I aim to form a proper and full coalition between the Conservatives and the Liberal Democrats. I believe that is the right way to provide this country with the strong, the stable, the good and decent government that I think we need so badly," he said.

Cameron also pledged to care for the needy and to "take everyone through with us on some of the difficult decisions we have ahead."

During Tuesday evening, details of government personnel began to emerge. Five Liberal Democrats will sit in the cabinet, close to a quarter of the ruling core, with Clegg as deputy prime minister.

Cameron's two most senior lieutenants were designated to top jobs, with George Osborne as chancellor of the exchequer, equivalent to finance minister, and William Hague as foreign secretary. Osborne, 38, is the youngest chancellor for more than a century.

Clegg's most senior and respected deputy, Vince Cable, becomes first secretary to the treasury, deputy to Osborne. Clegg's chief of staff, Danny Alexander, a member of parliament for a Scottish constituency, becomes secretary of state for Scotland.

The first foreign leader to call the new British prime minister was U.S. President Barack Obama, who the White House said "told the prime minister the United States has no closer friend and ally than the United Kingdom" and invited Cameron to visit the United States in the summer.

"I reiterated my deep and personal commitment to the special relationship between our two countries -- a bond that has endured for generations and across party lines, and that is essential to the security and prosperity of our two countries, and the world," Obama was quoted as saying.

Obama was followed by German chancellor Angela Merkel, who congratulated Cameron on his victory and also invited him to visit Germany.

"Only those who have held the office of prime minister can understand the full weight of its responsibilities and its great capacity for good," Brown said in his resignation speech, concluding his tenure a little short of three years and ending the longest spell of ruling by his center-left Labor party.

Following four straight general election defeats at the hands of Margaret Thatcher's Conservatives, Labor won the 1997 election and also the next two in 2001 and 2005 under Tony Blair, who was prime minister from 1997 to 2007 before he stepped aside to allow Brown into Downing Street.