Alistair Darling is regarded as one of Tony Blair's most trusted colleagues, despite keeping a foot firmly in the Gordon Brown camp.
Alistair Darling was transport secretary for four years
As the new trade secretary, he will work closely with his friend, the chancellor, and one of his key tasks will be to cut unnecessary red tape and stimulate business.
Mr Darling was given the sensitive transport portfolio in 2002 after the resignation of Stephen Byers following a number of controversies.
One year later, he was given the added responsibility of Scottish affairs still dealt with at Westminster.
The MP for Edinburgh South West was first elected to Parliament in 1987, after a career as an advocate and a short stint as a councillor, and was soon promoted to the front bench as a committed moderniser.
1987: Enters Parliament
1988-92: Opposition home affairs spokesman
1992-98: Labour City spokesman
1996-97: Shadow chief secretary to the Treasury
1997-98: Chief secretary to the Treasury
1998-2002: Work and pensions Secretary
2003-2006: Transport secretary
Appointed chief secretary to the Treasury in the wake of the 1997 election win, Mr Darling was said to have impressed officials with his ability to grasp even the most complicated brief.
He moved rapidly to put into place wide-ranging reforms designed to improve regulation of banking and financial services after the collapses of Barings and BCCI.
Within a few months, he had replaced Harriet Harman as social security secretary and responsibility for delivering Labour's welfare reforms.
In that post, which was renamed work and pensions secretary during his stint, Mr Darling was responsible for spending a third of the government's budget.
He has said that if he is remembered, he would like it to be "as the minister who began to eradicate poverty".
But he was one of the targets of angry pensioners who were outraged when their pensions were raised by only 75p last year.
The episode, one of the most damaging of this government's time in office, included a rebellion at Labour's conference in 2000.
As transport secretary, he argued it would take a long time to remedy decades of underinvestment in public transport, but his road-pricing proposals have sparked fierce debate.
Mr Darling's constituency in Edinburgh is a fairly middle-class one. Although he was not born in Scotland, he is said to feel Scottish.
Like Tony Blair, he went to boarding school - but it was an experience he did not relish.
Darling is loyal to Blair and close to Brown
He has said that people join the Labour Party and become MPs because they want to change things "for the better".
It is this motivation that makes him leave his family at home in Edinburgh each week to pursue his role as a minister.
Up until quite recently, one of the most famous things about Mr Darling was his insistence on wearing a beard, because commentators deemed facial hair to be not at all New Labour.
Rumours were rife that Mr Darling's whiskers were given their marching orders.
Eventually he did shave his beard off - despite the fact it was reputedly favoured by his journalist wife Maggie.
Like many other Labour front benchers, he has changed his mind significantly over the years.
Although anti-devolution in 1979, he had become a supporter by the time the second Scottish referendum was under way.
In opposition, he was once said to have been mounting a campaign against Rupert Murdoch's predatory pricing policy, but quietly ditched it when told of Mr Blair's bid to charm the press baron.
He also opposed a proposal by the then Conservative MP Nicholas Budgen to make the Bank of England independent of the government - although independence was one of the first acts of the Labour government on gaining power.