The showdown began when Big Ben struck noon.

David Cameron, elected Tuesday as leader of the Conservative Party, looked across the green carpet of the House of Commons at his adversary, Prime Minister Tony Blair. Their first public clash of wits was about to begin before a packed chamber.

It was Prime Minister's Questions, that most British of parliamentary rituals, in which Blair makes his weekly Wednesday noon appearance in the Commons to be questioned, shouted at, jeered and routinely accused of everything from ignoring genocide in Africa to contributing to traffic congestion in the British Midlands.

Would Cameron bash Blair over tax policy? Or perhaps the impasse over a European Union budget? "The first issue," Cameron began, "that the prime minister and I are going to have to work together on is getting the good bits of his education reforms through the House of Commons and into law."

Praising a Blair policy and promising cooperation was hardly the kind of talk that Blair got from four previous Conservative leaders. It signaled a new approach for the Tories, who are betting that the smooth and telegenic Cameron, 39, is their best chance of reconnecting with British voters after three consecutive electoral drubbings by Blair's Labor Party since 1997.

"It was a staggeringly assured debut," Andrew Gimson, columnist for the pro-Conservative Daily Telegraph newspaper in London, said in an interview. "I think once he started he found that he was enjoying it. And he made Blair look rather old and tired."

Cameron promised in his acceptance speech Tuesday that he would try to bring a new tone to British politics. "I'm fed up with the Punch and Judy politics of Westminster, the name-calling, backbiting, point-scoring, finger-pointing," he said, referring to the Gothic revival building where parliament convenes.

Early in his appearance Wednesday, Cameron pounced on an opportunity to challenge the session's combative atmosphere. Amid the typical hooting from lawmakers, Cameron turned to Hilary Armstrong, the Labor Party's chief whip, who was sitting in the front row heckling him, and accused her of "shouting like a child."

Cameron's calls for more genteel behavior don't mean that his tongue won't sharpen in future encounters. According to a column he wrote for the Guardian newspaper in 2002, which the paper reprinted Wednesday, Cameron sees value in the feisty atmosphere of Prime Minister's Questions.

"Yes, it is theatrical, even gladiatorial, with backbenchers waving and cheering like the crowds at the Circus Maximus. And that is the point," he wrote. "A prime minister or leader of the opposition who was slow-witted, corrupt or simply not up to the job would not survive."

In Wednesday's 30-minute question period, Cameron mixed silky calls for cooperation with equally smooth jabs at Blair that almost seemed like dinner-table teasing. When Blair disagreed with Cameron over aspects of education policy, Cameron said, "His approach is stuck in the past and I want to talk about the future." Then he added with a smile in Blair's direction, "He was the future once."

The line was met with knowing howls all around, partly because Cameron has more often been compared to Blair than to former leaders of his own party. Both men are self-proclaimed centrists who arrived on the political stage young: Blair was 41 when he took over the Labor Party in 1994 and 43 when he became prime minister.

Cameron, like Blair, is a polished and charismatic product of elite schools, having attended Eton and then Oxford University. And like Blair, he is adept at political imagery -- Cameron is often photographed riding his bicycle to work while many of his colleagues travel in chauffer-driven luxury cars.

Also like Blair, who is now 52, Cameron comes to office with an overwhelming mandate from his party. He won nearly 68 percent of the vote to defeat veteran David Davis, 56, for the leadership of the party.

While Blair and Cameron have differing views in many areas -- Cameron is far more skeptical than Blair about Britain's involvement in the European Union, for example -- Wednesday's first session appeared to be more about image than policy.

"He's quite good at the patter and the blather," Alistair Campbell, Blair's former press secretary, said to Sky News after Cameron's performance. "But it's not about presentation, it's about substance. Where is the substance?"

Prime Minister Tony Blair, left, hears surprising offers of cooperation from the new Conservative Party leader, David Cameron, right, during the usually contentious Prime Minister's Questions, a weekly session in Parliament.