The former weekend SAS man - he was in the special forces of the Territorial Army - is planning the assault on the Tory leadership with the meticulous detail of a Himalayan scaling party. He does not expect to be defeated. Asked whether he was worried, at 56, that he would be up against a baby-faced-38 year-old in David Cameron, he grinned like a piranha.
It is well known that his camp believes that Michael Howard is doing everything he can to stop Mr Davis winning, including delaying the contest to allow Mr Cameron time to catch up. Mr Davis grins again, being too wise to fall into that crevasse. He does not intend to attack Mr Howard. "When I play sports, I never question the rules."
So it is time to bring on the contenders? "Yeah," he said, almost gleefully. "We've got plenty of time." He picks them off on his fingers. "I don't know how many are there now ... Liam [Fox] ... fortyish, David Willetts, Theresa May did I hear ... and there's Ken."
Yesterday, Oliver Letwin, a former shadow Chancellor, said that he would back Mr Cameron if he stood. But Mr Davis is resilient. His self-confidence irritates some colleagues, but it is a quality that the Tory party probably needs to climb its own mountain back to power, however many tries it takes. It is a quality that helped him to rise from a slum flat in a hard council estate in London.
Mr Davis was born in York just before Christmas Eve in 1948, the illegitimate son of a single mother - his father ran away within days of discovering his mother was pregnant. Four years later, his mother moved to Tooting, in south-west London, when she married Ronald Alexander Davis, a shop steward at Battersea power station. The boy was adopted when he was 11, when he also passed the 11-plus exam.
He became a prefect at Bec grammar school, Tooting, and stood up to a gang from the 5X form - the O-level exam failures - when they beat up a boy for allegedly being gay. The boy, now married with children, and the gang have since been traced and recently corroborated the story.
Mr Davis was a "tough kid" at school with a reputation for "getting into scraps", said an old schoolmate. He broke his nose five times - three times playing rugby for his school second XV, once in a swimming pool accident, and again in a fight on Clapham Common.
He had a difficult relationship with his stepfather, although he christened his own son, Alexander, now 18, with his middle name. He revealed last month that he tracked his birth father down 30 years ago when his father was in his fifties, and does not know whether he is still alive.
The "back street bruiser" is a unique upbringing for a potential Tory leader (Mr Cameron is an Old Etonian) and gives him more authority than most to talk about reconnecting the Conservative Party with the ordinary people it needs to win back power. His speech today to the Centre for Policy Studies will be a dress rehearsal for the themes that will become familiar at the next election, if he wins the leadership.
"The Conservatives' top priority must be to improve the everyday lives of ordinary people," he said. "I will argue that Labour's policies have increased insecurity - pensions is the obvious one to point up there, but there are plenty of others: the over-reliance on targets, the target culture has a bad effect on policing and a poor effect on health care ... people sitting in ambulances so they don't break A & E targets, all that sort of stuff."
He also intends to answer those Tory leadership candidates, including Mr Cameron, who have tried to soften the Tory image by supporting the Government where necessary, particularly on reform of public services. Having claimed the scalps of Beverley Hughes and David Blunkett while shadowing the Home Office, he intends to take no prisoners now.
He rejected a frontbench post in opposition under William Hague and opted instead to become chairman of the Public Accounts Committee (PAC). He became a thorn in Labour's rump from 1997, and earned grudging respect from Labour MPs.
"Victims of the state are a whole series of people - people who end up with MRSA, people who have poor local policing and yobs on street corners, people who end up with their kids not getting a decent education at school, people whose life chances are poor, unable to get on - not as lucky as me if you like," said Mr Davis, who joined the TA to help pay for his university education at Warwick, which his parents could not do. "I was dead lucky," he said. "In a way I am a member of the privileged generation. My generation had huge social mobility - all those opportunities came for us. Those opportunities are shrinking now. Social mobility is going down. There are new glass ceilings in effect for people from the bottom of society.
"People feel frustrated, whether it is about being unable to buy their council house in London [because the right-to-buy discount has been cut] or because they are unable to get on because every career path needs a degree to get on and they haven't got one."
It seems unlikely that this group at the bottom of the pile in society would vote Conservative but Mr Davis is determined to try. He was a Thatcherite - Lady Thatcher appointed him her minister for Europe because he was a "sound" Eurosceptic - and he sees nothing inevitable in the blue-collar workers voting Labour or even Liberal Democrat. "I think if we write off sectors of the population, we don't deserve to win - blue-collar council estates, all ethnic groups, all parts of society."
There are two portraits of Gladstone, his political hero, on the walls of his office and none of Disraeli, in spite of the revival of "one-nation" Toryism. He explains Gladstone, apart from being a free-market liberal, was also a chairman of the PAC. "This chap gave me my chance in life," he joked.
Mr Davis does not intend to have a bonfire of the policies on which the Tories lost the election and he will keep the controversial "patient's passport", offering a state subsidy for anyone opting to go private for their health care. Mr Davis sidestepped another crevasse, however: "I don't have private health insurance," he said. "Couldn't afford it."
Does he think he would stand a better chance against Gordon Brown than against Tony Blair? "It's a different chance, is the truth," he said. "Brown has got more trust than Blair. If the economy becomes problematic, that will reflect on him. Brown is more of a socialist than Blair, so there will be natural blue water between us."
He added: "On matters like public service reform, Brown will be reluctant to do anything. He has been the impediment to the Government carrying out the reforms. If that is true, we will become the real party of public sector reform."
His wife, Doreen, stays firmly out of the limelight. They met at Warwick University where she was studying molecular science, and married in 1973, the year before their first child, Rebecca, was born, when Mr Davis was studying at the London Business School, and ran for the chairmanship of the Federation of Conservative Students, the right-wing outfit later disbanded by Norman Tebbit for being out of control.
Mr Davis was on holiday in Florida when Iain Duncan Smith sacked him as chairman of the party, suspecting he had been plotting against his leadership (in truth, no plot was necessary). Their daughter, Sarah, was doing shifts copytaking for newspapers in his Howden constituency for the Press Association, when one of his closest family friends, the former Tory MP Michael Brown of The Independent, began to spell out his name. "I can spell my father's name," she said.
Alexander is more likely to follow his father into the Westminster village when he leaves university. When he was attached to this newspaper for a summer work experience, Alexander witnessed Alastair Campbell being grilled by the Foreign Affairs Select Committee over the death of Dr David Kelly.
The next day, Alexander spent the day with Mr Campbell, a friend of Mr Davis, doing more work experience, and was at the private meeting in Downing Street when he discussed with allies how it had gone. Mr Davis asked his son, "And what did he say?" Alexander replied: "I don't think it's appropriate to tell you, father." It was the right answer, and the same reply he would have given if he had been asked to reveal all when, as a boy, he won a trip to Number 10 in the midst of a sterling crisis. He learnt that the Wilson government was about to ditch selective employment tax, but said nothing.
He is planning his annual trek across the north of England from coast to coast with Alexander this summer but, as he is running for the leadership of the Tory party, the isolation of the Pennines could be shattered by a media pack. "One of the things about doing the walk is I bump into people, none of whom know me. I may have a slight problem this time," he said.
23 December 1948, York
Bec Grammar School, University of Warwick (BSc joint Hons in molecular and computer sciences), London Business School (MSc), Harvard University (AMP)
Married Doreen Cook, 28 July 1973; one son, two daughters
1987-90: Director, Tate & Lyle, Globe Investment Trust
1987: Elected Conservative MP for Boothferry (1997 Haltemprice and Howden)
1993: Minister of State, Public Service and Science
1994: Minister for Europe, Foreign Office
1997: Chairman, Public Accounts Committee
2001: Chairman, Conservative Party
2002: Shadow Deputy Prime Minister
2003: Shadow Home Secretary
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