LONDON – Britain ushered in its first coalition government since World War II on Wednesday as a pair of rivals-turned-partners pledged to set aside their deep policy differences and tackle the country’s disastrous budget deficit.

With handshakes, smiles and a sprinkling of jokes, newly minted Conservative Prime Minister David Cameron and his Liberal Democrat deputy Nick Clegg showcased their pact in Downing Street’s sun-dappled garden. “This is what the new politics looks like,” Clegg said.

Cameron and his center-left partner pledged sweeping reforms to Parliament, civil liberties laws and ties to Europe as they made joking reference to the years they spent sniping at each other.

Cameron acknowledged he had once told an interviewer the best joke he had ever heard was “Nick Clegg.”

“Did you really say that?” Clegg said, pretending to walk away from the podium before Cameron comically implored him to come back.

The one-time foes banded together after Britain’s election last week denied all parties a majority – leaving the country with its first hung Parliament since 1974.

The Conservatives won the most seats but needed a coalition with the Liberal Democrats to oust the Labour Party after 13 years in office.

Voters struggling during a dismal recession gave no single group a mandate, and many people were left enraged at all politicians after an expense scandal last year in which lawmakers were caught making claims for everything from pornography to chandeliers.

Clegg and Cameron vowed that their partnership would stick so they could deliver the changes voters demanded.

They said their pact will hold until Britain’s next national election, and named May 2015 as the date for that vote.

“Until today, we have been rivals. Now we are colleagues,” said Clegg, the surprise upstart of Britain’s election campaign, who won a newly enhanced profile even as his party lost seats.

Clegg will be charged with political reforms, including looking at fixed parliamentary terms. And when Cameron – whose wife is expecting their fourth child soon – is away, Clegg will be in charge, with duties that will include standing in for the weekly and often raucous prime minister’s question time.

Conservatives and Liberal Democrats are divided on many issues, including ties to Europe and election reform, but each side has made some concessions to make the coalition work.