Ex-SAS man David Davis has been at Westminster long enough to know that, in politics, the motto "Who dares wins" is not always the most reliable guide to achieving success.
Mr Davis stood to be Tory leader in 2001 but withdrew after the first round
The shadow home secretary's decision to resign as an MP - with the Tories looking a good bet to win the next election - shocked most observers.
But, after cruising to victory with 72% of the vote, his gamble paid off - giving him, he said, a "clear mandate" to speak out against the government's plans to detain terror suspects for up to 42 days without charge.
Clearly angry at Gordon Brown's narrow win over the issue in the Commons, he forced a by-election to win back the Haltemprice and Howden seat he had held since 1997, having previously represented the Boothferry constituency since 1987.
In typically tough-talking style, he said it was "time to make a stand".
His opponents said his resignation was childish and pointless, his supporters that it was principled and courageous.
Whatever one's take, it was an unusual move by a complex and - in Tory terms - unusual man.
Born: 23 December 1948
Education: Bec Grammar School, Tooting; Warwick University; London Business School; Harvard University
Family: Married with one son and two daughters
Entered Parliament: 1987
Constituency: Haltemprice and Howden, since 1997
Most recent post: Shadow home secretary, since 2003
Amid an opposition frontbench noted for the privileged backgrounds of many members, Mr Davis's origins were distinctly working class.
He was born on 23 December 1948 to a single mother on a council estate and was adopted by a Polish Jewish print worker with strong trade union links.
He went to a state school and to Warwick University, and his communist grandfather was one of the leaders of the 1936 Jarrow march.
Mr Davis has a reputation as a no-nonsense right-winger, and his super-fit, action-man image is aided by a three-times broken nose - once when playing schoolboy rugby, once in a swimming pool accident and finally, apparently, in a fight on Clapham Common.
He is a former member of the Territorial Army's SAS and an extreme sports enthusiast who enjoyed cartwheeling out of aircraft into parachute jumps, mountain climbing and flying light aircraft.
Mr Davis, a former businessman, has had almost as eventful a political career.
He joined the whips office in 1990 before being made a junior minister for public service in 1993.
In 1994, he moved to the key post of minister for Europe at the Foreign Office, a post he held until the 1997 election.
He entered the Tory leadership contest in 2001 but withdrew after faring poorly.
Mr Davis was appointed chairman of the party in the same year. But in 2002, while out of the country, he was removed from this role by leader Iain Duncan Smith, and given the role of shadowing Deputy Prime Minister John Prescott.
Seen as a demotion, it was an episode which caused some deep frictions inside party ranks - Mr Davis was seen at the time as the biggest threat to the then struggling Mr Duncan Smith's hold on his job .
As it was, Mr Duncan Smith was effectively forced out by Tory MPs the next year, but after much speculation, Mr Davis decided not to run against Michael Howard for the leadership. When Mr Howard won unopposed, Mr David was promoted to shadow home secretary.
Mr Davis stayed in that role for more than four and a half years - a period which also included the election of David Cameron as Conservative Party leader in 2005.
Before the contest to find a successor to Mr Howard began, Mr Davis was seen as the clear favourite, and as a representative of the Thatcherite, Eurosceptic views held by many grassroots Conservatives.
But a poorly received speech at the 2005 party conference was eclipsed by a slick, unscripted performance by Mr Cameron, then only a junior member of the shadow cabinet.
Mr Davis came second in a vote by Tory MPs and was eventually beaten in a run-off among the wider membership.
Upon winning, Mr Cameron kept his rival as shadow home secretary and their relationship since has been notable for a lack of any obvious acrimony.
Mr Davis has positioned himself as being tough on law and order but, perhaps more importantly, as a defender of civil liberties against an overbearing state.
His targets have included plans for ID cards, a DNA database and changes to jury trials.
In recent months he has been the most high-profile parliamentary opponent of the government's plans to detain terror suspects for up to 42 days without charge.
Just the day before the 42-days vote in the Commons, he posed outside Parliament at a Liberty arranged photocall with fashion designer Vivienne Westwood and actress Honor Blackman to protest against it.
The government's narrow win clearly upset Mr Davis. In his resignation statement, he said it would be a "monstrosity of a law" if it also clears the House of Lords.
And although sources suggested that some other leading Conservatives did not share his zeal on this point, there was no suggestion this has anything to do with his resignation.
However, despite winning the by-election Mr Davis has admitted it is unlikely that Tory leader David Cameron will invite him back onto the party's front bench.
"I took on board that I would lose my shadow cabinet post and probably my shadow cabinet future," he said. "I accept that."