The prime minister, Tony Blair, completed his reshuffle on Thursday following the movements which came in the wake of Peter Mandelson's resignation.

Among the appointments announced on Thursday, George Foulkes, the junior minister at the Department for International Development, is promoted to become minister of state at the Scotland Office - where he replaced Brian Wilson, the new Foreign Office minister.

Foulkes is replaced at DfID by Chris Mullin, whose post at the Department of the Environment, Transport and the Regions is filled by government whip Bob Ainsworth.

The reshuffle was prompted by the resignation of Peter Mandelson which resulted in Scottish secretary Dr John Reid becoming Northern Ireland secretary. His appointment followed a 45-minute meeting between the cabinet minister and Tony Blair in Number 10 on Wednesday night.

Downing Street is said to rate the new secretary of state, who has been used extensively in media interviews when things have been tough for the government - most notably during the fuel crisis.

Reid was replaced at the Scotland Office by Helen Liddell, the current energy minister dubbed "Stalin's granny", who was the Scottish education minister before devolution. She and Foulkes will mount an aggresive campaign against the SNP over coming months.

Liddell was replaced at the Department of Trade and Industry by Foreign Office minister Peter Hain. Brian Wilson, Reid's deputy at the Scotland Office, takes up Hain's post. Hain's apparent "demotion" is being attributed to his opposition to the "son of Star Wars" project which, some suggest, has strained relations between the Foreign Office and Washington.

Reid, a chain-smoking, teetotal, straight-talking Scot, was brought up in a mining village in the West of Scotland - the breeding ground of gut socialism.

Once describing himself as a "mongrel", his grandparents included both staunch Scottish Presbyterian stock and Irish Catholic immigrants.

He was educated at a Catholic school under the guidance of a strict headmaster who, Reid says, "saw his role in life as dragging the working class Catholic population up by the scruff of the neck".

An early rebel, he shunned the idea of university, choosing instead to try his hand at a music career.

"My parents encouraged me to go to university but I rebelled. I was in a rock group, and later on the folk circuit, and couldn't see what the big deal was about getting education," he said in an interview in 1995. "As a result, I have done all sorts of jobs: labouring, working in the roads, laying gas pipelines, and in the insurance industry, where I ended up advising very rich people how to avoid Denis Healey's estate duty."

He later returned to education, first joining the Open University, before taking up a full time degree at Stirling University - where he eventually secured a PhD in Economic History.

Whilst at Stirling, Reid, an early ally of Gordon Brown who has switched his allegiance to the Blair project, entered student politics. It was not, however, until the late 1960s that he finally decided to pursue a career in active politics.

"What really brought me into politics was the great storm of 1968," he said in the 1995 interview. "I was covering the storm damage for an insurance company and was staggered by the depths of poverty and despair I came across, particularly amongst old people and very young families. The level of poverty still existing in the 1960s - and in some areas now - was beyond even what I had seen in a pretty working class upbringing."

After joining the Labour Party, and following a brief flirtation with the Scottish communist party in 1975, Reid became a full-time officer in the Scottish Labour Party - eventually joining Neil Kinnock's private office in 1983.

He entered parliament in 1987, and, after a period as Joan Lester's deputy on Children's Affairs, joined the defence team under Martin O'Neill.

Following Labour's victory in 1997, Reid took up the post of minister for the armed forces - a post which he greatly enjoyed and where he secured the respect of senior MoD officers.

Whilst at the MoD he was a crucial figure in the strategic defence review and gave an early undertaking to probe cases of Gulf war syndrome.

After a spell as transport minister, Reid was promoted to the cabinet to fill the post of Scottish secretary following the decision by Donald Dewar to become Scotland's first minister.

No sooner was Reid installed in the grandeur of Dover House was his new post dubbed a "non-job".

His time at the Scotland Office was not easy - with strong rumours of angry spats with the late Donald Dewar and controversy following the lobbygate affair in which his son Kevin was implicated.

In December, he narrowly escaped sanctions over his decision to send House of Commons research staff to campaign in the elections for the Scottish parliament.

Reid had been tipped as a potential defence secretary, although the post - which he made no secret of coveting - eluded him when it was given to Geoff Hoon following the departure of George Robertson.

As a Catholic, Reid will have to work to ensure he secures the lasting support of the unionist camp. Ulster Unionists and the province's first minister, David Trimble, have let it be known that they support his appointment.

He is seen as a safe pair of hands, who, in the words of Roy Hattersley, will do the job "well, but not spectacularly well" - a description which could equally be applied to Trimble himself.

The MP for Hamilton North and Bellshill, Reid becomes the first Scot to occupy the post of Northern Ireland secretary.

His immediate task will be to move the peace process forward at a sensitive time in Northern Ireland. The pressure, though, will also fall on the shoulders of Tony Blair - who will have to work hard with his new secretary of state to broker a deal in the coming crucial days.