Cameron leaves with the line: 'I was the future once'

In his final appearance at prime minister's questions in the House of Commons, Cameron recalled his own famous line from his first appearance in the theatrical weekly sparring session 11 years ago.

Then the newly elected Conservative opposition leader, he taunted embattled Labour prime minister Tony Blair: "I want to talk about the future. He was the future once."

That vision of change launched Cameron on his way to becoming prime minister in 2010 -- the youngest in 200 years.

Six years later, he is leaving office under the shadow of Britain's impending exit from the European Union -- a career ending dramatically with his failure to keep Britain in the bloc.

The convivial atmosphere in parliament contrasted sharply with the divisions in the country exposed by the referendum on which he had staked his reputation.

"You can achieve a lot of things in politics," Cameron, 49, said, before a packed lower house.

"And that, in the end -- the public service, the national interest -- that is what it's all about.

"Nothing is really impossible if you put your mind to it. After all, as I once said, I was the future, once."

Conservative backbenchers stood to cheer and applaud him as he left the chamber, turning to wave to his wife Samantha and children watching from the gallery.

Colleagues slapped him on the back and hugged him as he left, shaking hands with Speaker John Bercow as he went.

The response from opposition MPs was polite, but not warm.

"The prime minister's legacy will undoubtedly be that he has taken us to the brink of being taken out of the European Union, so we will not be applauding his premiership on these benches," said Scots Nationalist MP Angus Robertson.

With his successor Theresa May sat beside him, Cameron told MPs: "I will watch these exchanges from the backbenches, I will miss the roar of the crowd, I will miss the barbs from the opposition, but I will be willing you on."

One of the set-piece occasions of parliament, prime minister's questions is rough-and-tumble political theatre at its best -- as Cameron himself recalled.

He recounted how, when he was the opposition leader, he met mayor Michael Bloomberg in New York.

"No one had a clue who I was until eventually someone said, 'Hey! Cameron! Prime minister's questions! We love your show!," Cameron said, attempting a US accent.

Cameron said he would miss Larry, the Downing Street cat who will be staying on in the prime minister's residence.

He said he wanted to put to rest "the rumour that I somehow don't love Larry. I do and I have photographic evidence to prove it", holding up a picture.

"Sadly I can't take Larry with me: he belongs to the house and the staff love him very much -- as do I."

Amid the tributes, some MPs made suggestions for his future role, noting vacancies as England's football manager, the presenter of BBC motoring show Top Gear and the judge on a dancing contest television show.

The final question was given to Conservative heavyweight Kenneth Clarke, the 1990s finance minister.

He urged Cameron to keep speaking from the backbenches as Britain negotiates its exit from the European Union.

"We need his advice and his statesmanship as much as we ever have," Clarke said.

To laughter, Cameron recalled that Clarke's first act on becoming finance minister was to sack him as a Treasury special advisor.