Gordon Brown could be Chancellor soon. He lives on yoghurt, bananas and 18-hour days, and declares everything outside politics a waste of time - except football, now and then
Gordon Brown's home in Scotland is a square, stone Victorian house above the village of North Queensferry. It's Saturday afternoon and work is over for the day. I ask him if he'll take off his suit jacket for a photograph. He goes upstairs reluctantly, and comes back with a navy cashmere sweater draped round his shoulders. I then ask if he could remove his tie. "I never take off my tie," he grumps.

The house has a panoramic view of the Firth of Forth, and Brown stands on the front lawn and uses binoculars to watch the procession of tankers, trawlers and yachts which crawl across the water. He bought the house six years ago but inside it still has the feel and appearance of a rented property. He spends Friday and Saturday nights alone here.

Breakfast is eaten in the kitchen from the basic supply of groceries delivered weekly: instant coffee, milk, yoghurt and bananas, his favourite fruit. The large, square sitting room is dominated by a television on which Brown watches football on Sky, or a rented video. Only a few curling, unframed family photographs on the mantelpiece strike any personal note; otherwise the walls are bare. There's an upright piano in the dining room and he can still pick out a tune. He learnt to play at school. He likes the Beatles, Elvis and the Scottish rock band Runrig.

This is where he belongs. Driving through his constituency (Dunfermline East) to North Queensferry, he points to the farm where his grandparents lived. As a son of the Manse growing up in Kirkcaldy, where his father was the Church of Scotland minister, he attended church twice a day on Sundays. "Going to church leaves its mark, and I suppose that's where my principles come from," he says. His parents, now retired, live in Aberdeenshire; he usually spends Christmas with them.

He knows the place intimately, so when he sees a shop that has been boarded up, he knows who has gone and wants to know why. He still supports Raith Rovers, where he and his elder brother John used to sell match programmes.

He goes on holiday with John and his other brother Andrew and their families to a hotel in Cape Cod. Brown likes America and enjoys browsing in the politics section of his favourite New York bookshop, Barnes and Noble, or shopping for seemingly identical navy suits in Saks Fifth Avenue.

His few close friends are Scots: Alastair Moffat, a colleague from his days at Scottish Television; Murray Elder, adviser to Donald Dewar, dates back to primary school; Colin Currie, an Edinburgh consultant in geriatrics.

Brown has always been discreet about his personal life. Girlfriends have had to slot into his busy schedule and they've probably never impinged on the emotional core of his life, which revolves around politics.

His principal relaxation is sport, especially rugby. "I go to all the internationals. I would have liked to play myself at any level but contact sports are out because I lost the sight in one eye playing rugby when I was 16. It was just an accident in the scrum but no one realised there was a problem until weeks later. I've had several operations but nothing more can be done."

Last summer he was able to fit in quite a few Euro 96 games, and he declares: "The only irritating thing about my job is having to work on a speech when I want to go to a game."

Brown regards almost everything else outside politics as a waste of time. "I don't like formal dinners or social activities in general." His private "waste of time" list includes Parliament. "During Question Time I often have to sit in the Chamber for an hour and may speak for only 30 seconds. The place is geared towards eloquence rather than the pursuit of excellence."

Brown works an average 18-hour day, six days a week and every minute has to count. During the week he sleeps in a one-bedroom flat, five minutes from the Commons. He wakes up with the 6am BBC news, and then there'll be an early morning call from Tony Blair to discuss Labour's issues and agenda for the day before he walks round the corner to the Living Well gym to swim and pound the treadmill for an hour to maintain his recent weight loss of a stone.

By 9am he is at Labour's media centre at Millbank Tower. After half- an-hour during which Labour's press line for the day is decided, he makes for Plods, the cafeteria inside the Houses of Parliament favoured by the on-duty police. Once again he confines himself to yoghurt, coffee without sugar and diet coke.

His office is a small room filled with tottering piles of books and files. Phones ring constantly on the line of utilitarian desks under the stone fan-vaulted ceiling. "I'm the oldest in the office by a long way," says Brown, who was 46 on 20 February. "Most of the staff are in their late twenties or early thirties. I used to have only one researcher, but now we've geared up for the election there are six full-time."

If Brown runs Britain's economy the same way he runs his office there will be no frills and no fat cats. As a member of the Shadow Cabinet, Brown gets pounds 22,000 a year to pay for staff in addition to the secretarial allowance given to all MPs. There is also a sensitive "blind trust" which helps to fund the running of the shadow Chancellor's office. No one will say how much it contributes or who the contributors are.

His personal finances are no secret, however: he earns pounds 15,000 a year for a weekly column in the Daily Record. "Last July I voted against the Commons 26 per cent pay increase. I accepted a 3 per cent rise, the same as the public sector workers, so I earn around pounds 35,000." He has no official car, no lucrative directorships, and no highly-paid wife like Cherie Blair.

In the Commons, Brown rushes between meetings, always carrying a sheaf of papers and files under his arm and listening to briefing from his advisers on the next appointment. His fixed diary items are the Wednesday afternoon meetings of the shadow cabinet and he sees Tony Blair alone nearly every morning. If he isn't working in the Commons, his evenings are taken up by political engagements such as his speech last week to the Business Forum where he outlined his plans for the Treasury and the Bank of England.

On Fridays Brown usually flies to Edinburgh around midday. Airports are high on his "waste of time" list and he plans his arrival to coincide with the final boarding call. In the car on the way to Heathrow, while the driver performs miracles of traffic dodging, Brown simultaneously uses a mobile phone and goes through the pile of papers on his lap, jotting notes in the margin. He rings his constituency agent who has just been told she has cancer. His words are quiet, kind and supportive. The shadow Chancellor never checks in luggage, carrying all he needs in a black holdall. As soon as he's buckled into his seat he concentrates on his papers, writing in pencil in block letters key words and phrases for this afternoon's speeches. When lunch arrives he hoovers it up, including a quite disgusting slice of cheesecake. We happen to be travelling on Valentine's Day and he ruefully passes me a heart-shaped chocolate from his tray. He says tersely: "I haven't sent any Valentine's cards and I don't know if I received any because I don't open the post."

He does not own a car and prefers to be driven so that he can write and make calls on the move. He is met at Edinburgh Airport by Rona Whyte, his constituency secretary, in her white saloon car. Brown and Rona plunge into a discussion about his election campaign. "There will be about 60 people working on the ground here. We're doing leaflets, posters, the lot. It's a mistake to assume victory."

The traffic is now heavy and Brown begins to fret: "I'm keeping everyone waiting," he says. When we finally cross the Forth Bridge, he cries: "Freedom! My constituency begins here. There's Rosyth naval base. I'm still angry I couldn't prevent the Government from closing it. This area depended on those jobs. Parts of my constituency have an unemployment rate of 20 per cent."

Brown's first stop is at Lauder College to open a new building. He runs his fingers through his hair, straightens his tie, leaps out of the car and delivers a faultless 10-minute speech without notes. He is much more relaxed in Scotland and it is noticeable how he listens rather than talks to the students and staff. Everyone calls him "Gordon". Rona smoothly extracts him as soon as she can, because he is running an hour late. Next stop is in Cowdenbeath, where Brown presents NVQ certificates in business administration and IT to government trainees. The quality of the trainees, who were all previously unemployed, is incredibly high and nearly half of them have now got a job. Ironically, if all the Government's retraining schemes were as successful as this, Labour wouldn't have a leg to stand on.

In the late afternoon Brown begins the first of three surgeries he holds in the evening, and there are five more on Saturday. He explains: "The constituency is made up of small towns and villages so I hold monthly surgeries in 11 community centres around the area. Most of the people who come to see me don't have transport." Three or four come to each venue, and mainly they want their MP's help with benefit payments or redundancy problems.

For a man who presents such a dour face to the world he is capable of inspiring real warmth. He doesn't project the smooth, shallow charm of many politicians, relying instead on his own rather serious personality which fits in with the local culture. He is one of them. An MP who laughed, slapped backs and told jokes would still be voted into this Labour stronghold - but he would not be liked or trusted.

The shadow Chancellor is a private man with a solid background, who keeps his thoughts and feelings to himself. Brown won't talk about his boss except in standard phrases like "close working relationship", but he did feel betrayed by the leadership battle after John Smith's death in 1994 when he was forced to adopt the moral high ground by not contesting the leadership and splitting the party.

For nearly two years he was morose and gained weight but now he has literally worked himself out of his personal slough of despond and emerged as fitter, leaner and tougher. At the moment Blair and Brown are allowing no cracks to appear in their public dealings with each other, despite reported differences over the windfall tax, Scottish devolution and the top rate of income tax.

Nevertheless, he is conscious that chancellors, just like football managers, do not last long in the job. Brown would do well to use the platform of Number 11 - assuming he gets there, of course - to plan his next political career move.