In the middle of one of his regular assaults on worldwide football domination, Alex Ferguson thought Cathy, his long-suffering wife, deserved a break. With all the work he was doing at Manchester United, not to mention the autobiography he was writing and the race meetings he had to attend to watch his horse in action, she had hardly seen him. So he booked a romantic 48 hours in Rome, on one of those rare weekends when the league programme is postponed for international fixtures. And what did they do there? Visit the Vatican? Take a trip round the Coliseum? No, he took her to a football match featuring the local team.

"I picked up the paper," he recalls. "And said `Oh, look, Lazio are playing this afternoon, why don't we go and watch them?' So we did." And was England's most famous football manager recognised as he queued to buy his tickets at Rome's Olympic Stadium? "Nah," he says. "I didn't have to queue. I'd arranged tickets before we left England. I'd wanted to see Lazio for a while, that was one of the reasons I'd suggested Rome."

Not for nothing does the registration number on Ferguson's car spell out the word "FAN": this is a man obsessed with football, who, according to one old friend "sees football pitches on the ceiling when he lies in bed at night," and who likes nothing better than to plunge deep into football statistics, pouring over facts, figures and trivia.

In a few days' time he might well discover an entire chapter of British football history dedicated to him. With the Premiership and the FA Cup now in the bag, Ferguson will lead Manchester United in an assault on the European Champions League aiming for a treble, never before achieved by an English team. For someone as keen as he is on the history, significance and meaning of the game, there could be no greater opportunity.

Ferguson signed a contract recently which, at just over £1.25 million a year, makes him the highest-paid manager in British football history. This merely gave financial recognition to what even his most virulent detractors (and he has plenty) would readily accept: when it comes to football management he is without peer. True, others may be tactically superior, or his equal in developing a squad mentality, or can match him for dressing-room inspiration, but none has his record of sustained pre-eminence, none has ever been in a position to win the three biggest club trophies in one season. More significantly, none has the kind of resonance he enjoys outside the game.

His admirers include business leaders, who are fascinated by his achievement. They want to understand how Ferguson, now 57, he has remained for 20 years so pre-eminent in a profession which generally offers the job security of a dodo farmer. In short, they want to learn what methods he has employed to become "the best man-manager in Britain today". Sometimes, after a big game, there can be upwards of 50 people in his office, all anxious to be near the epicentre of success.

It is a modest office for the most significant employee in a company recently valued at over £650 million. From here, for the last 12 years, he has been plotting, scheming, buying, selling; a decade and a bit which has seen the departure and arrival of four Liverpool managers, five England bosses, and 11 unfortunates in the ejector seat known as Manchester City. His desk is a mess of papers, statistics, books, pictures of his grandchildren, a tottering Himalaya of videos. Behind him a picture window looks out across the training pitch where his assault on the treble has been planned.

But in front of him is perhaps the most significant pointer to his working methods. It is a huge flipchart, on which is written the names and ages of every player signed to Manchester United, from the international superstar Ryan Giggs to the young apprentice Ryan Ford. There are dozens of names (Ferguson employs over 60 professionals) and alongside each he has written comments about their current fitness, or to which club he has sent them temporarily on loan. Ask about any of them, and he can give you a precise breakdown of their skills, ability, character, chances.

"Some of these lads won't make it here," Ferguson says. "But I tell you what, they'll have a good career in football, I promise you that. Because of what we have taught them here." This close involvement in the detail is symptomatic of his entire method. From the earliest days of his managerial career in Scotland, with energy to burn, he has immersed himself in every aspect of his clubs.