Ken Clarke was home secretary and chancellor
Date of birth: 2 July 1940
Former chancellor, currently on the back benches
Education: Nottingham High School; Caius College, Cambridge
Family: Married, one son, one daughter
On his party's future: "We must raise the level of public debate in Britain. We must seek to avoid excessive use of slogans and mere abuse. We must set out a vision for the public as to how Britain can be better governed not just in terms of policies but in terms of a proper trustworthy system of accountable governance."
What the press say: "He is bitterly opposed by Eurosceptics but still has the political clout and 'bloke appeal' with voters to attract support from Tories who put winning the next election above purity of policy," Colin Brown, The Independent.
Despite no longer sitting on the front bench, Kenneth Clarke remains one of the Conservative Party's most senior and important figures.
Famed for his love of cigars, jazz and classic cars, the clubbable former chancellor is seen as a true big hitter who is still well regarded in the country. When he stood for the party leadership in 2001, opinion polls suggested he was most popular Conservative politician with the British people.
Mr Clarke is one of the few remaining members of John Major's government still in the House of Commons. Another is his potential leadership rival Sir Malcolm Rifkind, who returned to the Commons at this year's general election.
Mr Clarke is one of the most ardent supporters of Europe and the euro among current MPs - a stance which may have scuppered his two previous leadership bids.
Since becoming an MP in 1970, Mr Clarke has risen steadily up the Conservative ladder.
Within two years of his election he was an assistant whip, rising to whip and then becoming a junior spokesman on the opposition benches.
Born July 1940
MP for Rushcliffe since 1970
Health Secretary 1988-90
Education Secretary 1990-92
Home Secretary 1992-93
Chancellor of the Exchequer 1993-97
When Margaret Thatcher led the party to victory in 1979 she appointed Mr Clarke to the post of junior transport minister.
Over the next 10 years, he served as a junior minister in the departments of health, employment and trade and industry.
It was not until 1988, that Mr Clarke was promoted to the cabinet.
As health secretary, he was given the job of driving through controversial and far-reaching reforms of the NHS, including the internal market.
When John Major became leader he moved Mr Clarke to education and later the Home Office.
After the events of Black Wednesday, the resignation of Norman Lamont and the decision to leave the ERM, Mr Clarke was made chancellor.
It was as chancellor in the Major years that much of Mr Clarke's reputation and standing rests.
His period in charge of the Treasury saw interest rates, inflation and unemployment all falling.
CV: Ken Clarke, 65, ex-chancellor, currently on back benches
Key Quote: "We search for leaders who will be seen by the public as prime ministers in waiting. Oh boy, have you kept me waiting."
Best joke: "David Willetts keeps telling us that we will all need to work harder and retire later. Well, Mr Willetts, sir, I will do my bit."
Ovations: 20 rounds of applause and a two minute standing ovation finale
Speech length: 23 minutes, 44 seconds
Name drops: One Thatcher, but mostly about his own record
Nick Assinder's verdict:
Self-styled 'biggest beast' says time has finally come
Despite the economy's health, Mr Major's Conservatives - riven by splits over whether the UK should join the European single currency - suffered a huge electoral defeat in 1997.
Once the defeated Tory leader threw in the towel, Mr Clarke was one of the first to enter the leadership race.
Coming from the left of the party, and being one of the most pro-euro Conservative MPs, he lost out in the end to the youthful and more Eurosceptic William Hague, who benefited from the backing of Lady Thatcher.
Mr Clarke headed to the backbenches, taking on some company directorships and the deputy chairmanship of British American Tobacco.
He threw his hat into the ring again in 2001 after William Hague resigned, making it to the final round.
But Mr Clarke's hopes evaporated when the poll was opened up to party members, a majority of whom opted for Iain Duncan Smith.
He returned again to the backbenches, deciding not to stand against Michael Howard in 2003.
Mr Clarke's opposition to the Iraq war kept his name in the headlines and he has never been far from leadership speculation - despite the fact that he will be almost 70-years-old by the next general election.
He has said he still wants to be prime minister, but has no interest in leading a Tory party that is not prepared to occupy the centre ground.
He has also been more critical of Europe in recent times, saying he does not think Britain could join the euro with "complete security and confidence" for 10 years.
Mr Clarke's pro-euro stance had been seen as an obstacle to him standing.