By Mark Davies BBC News Online political reporter

Gordon Brown was no longer the potential prime minister, the betrayed friend or the dour iron chancellor with a penchant for prudence.

He was a grieving father and a caring husband, heartbroken at the death of his baby daughter Jennifer earlier this year.

For once in the chancellor's life, politics was very much at the back of his mind.

There was widespread sympathy for the Browns after the death of their daughter

Having returned to work at the end of January, Mr Brown, 51, is now preparing a Budget which comes amid the most difficult days the Labour government has faced.

It goes without saying that the death of his daughter will have changed Mr Brown. Famed for seeing politics as the main focus of his life, it is unlikely that the chancellor thinks that way anymore.

Mr Brown was born in Glasgow on 20 February 1951, the son of a Church of Scotland Minister in the small Fife town of Kirkcaldy.

At 12, he was canvassing for Labour and by his 20s he was a leading political activist in Scotland.

He achieved a first class degree in history from Edinburgh University, where he went on to complete a PhD.

Mr Brown's early career was spent lecturing, working in television and making a name for himself in the Scottish Labour Party.

Blair link

His first attempt to enter Westminster, for Edinburgh South in 1979, was thwarted by the present Tory spokesman on foreign affairs, Michael Ancram.

Mr Brown's supporters say Mr Blair broke a pact to allow their man a free run at the leadership

But in 1983, he took Dunfermline East, a new constituency including Rosyth naval base, pit villages and coastal towns.

Entering Westminster, he came to share an office with the newly elected MP for Sedgefield, Tony Blair.

Within four years, Mr Brown had gained his first frontbench post as shadow chief secretary to the Treasury.

He became shadow chancellor under John Smith's leadership in 1992.

And the death of Mr Smith in 1994 led to one of the longest-running sagas of Westminster life over an alleged agreement broken by Mr Blair.

No deal

If you don't know the drill by now, it goes like this: Mr Brown's supporters say Mr Blair broke a pact to allow their man a free run at the leadership.

Blair broke alleged pact

Mr Blair's supporters say such a deal never existed and that their man was a much more likely future prime minister anyway.

Endless newspaper columns have been devoted to the rift. Mr Brown even tried to kill off the story by saying Mr Blair was "his best friend in politics" in an interview last year.

Part of the reason why the speculation persists is that there is another alleged agreement: that Mr Blair will one day stand down in favour of the chancellor.

But if Mr Brown's leadership ambitions were at least temporarily thwarted in 1994, he continued his devotion to politics.

During the 1997 election campaign, he is said to have worked an average of 18 hours a day, six days a week after running on a treadmill for an hour each morning.

Praise

This devotion to his career was underlined by a comment by Mr Brown's former girlfriend of five years, Princess Marguerite of Romania, the eldest daughter of ex-King Michael of Romania, who said a relationship with him was "politics, politics, politics".

Ministers with expensive plans on their minds are being warned that the chancellor has lost none of his fondness for prudence

In government, Mr Brown is undoubtedly Mr Blair's most able minister. As chancellor, he has won widespread praise for masterminding Britain's economic stability.

Following Labour's election victory last year, the chancellor had a relatively quiet time and he and wife Sarah - the couple married in 2000 - prepared for parenthood.

His pre-Budget report received a cool reception, while in the wake of 11 September, he took a back seat as the prime minister strode the world stage.

And then in January he put politics totally out of his mind. First there was the birth of Jennifer, which revealed Mr Brown's softer side. Then, of course, there was the tragedy which followed.

Since he returned to work, Mr Brown has been concentrating on the Budget and this summer's spending review.

Ministers with expensive plans on their minds are being warned that the chancellor has lost none of his fondness for prudence.

Strong support

The ground has also been carefully prepared for potential tax rises aimed specifically at the NHS.

And Mr Brown has remained largely unscathed by the rows and splits which have beset the prime minister in recent weeks.

There is no doubt he still has his sights set on Mr Blair's job.

He has strong support in the party, with every reshuffle of ministers analysed for its potential effect on the Brownite power base.

But the emergence of David Blunkett as a potential rival as a future Labour leader means Mr Brown's ambitions are by no means assured.

So his Budget will, as ever, play a big part in what happens in the future.