So it is with Manchester United. They must feel entitled to their treble now, after all that hard work, but should beware the conviction that it is theirs by divine - or even Fergie's - right. I was in Manchester on Friday, and every United fan I met was brimming with confidence. Neither Newcastle United nor Bayern Munich would stop them now, they assured me. Even the wise David Sadler, a member of the 1968 European Cup-winning team, told me he believed the trophy was destined for Old Trafford again.
Much has been written about United's triumph in 1968, when they beat mighty Benfica at Wembley to become the first English winners of the European Cup. We have read about the heart-stopping moment late on, when, at 1- 1, Eusebio seemed certain to score, only to be denied by Alex Stepney. In extra time United scored another three, presenting Matt Busby with his Holy Grail. But, in some respects, the more significant game was the semi-final, against Real Madrid. For Real - while no longer the team of Puskas and Di Stefano - were still the most successful club side in Europe. Yet they had a healthy respect for Busby's team. Indeed, before the Munich air disaster 10 years earlier, the powerful Real president, Senor Bernabeu, after whom the stadium is named, had tried to make Busby his manager.
In the first leg, at Old Trafford, United beat Real 1-0. The goal was scored by the man David Sadler describes as the most talented footballer he has ever seen, let alone played alongside, a wizard, a sorcerer, a genius - the incomparable Nobby Stiles. Just kidding. It was, of course, George Best, with whom Sadler had a special relationship, for they were in digs together for years, with the indomitable Mrs Fullaway in Chorlton.
Those of a certain age, though agog at the skills of Giggs and Beckham, are adamant that Best played at a more rarefied level. "In training," Sadler told me, "they had to devise ways to get the rest of us involved. In five a side, nobody could get the ball off him. So we played two-touch, where he had to pass the ball, or even one-touch. But, even in one-touch games, he would knock it against you, which would count as your touch, and then pick it up again."
Not even the remarkable Best could lift United in the first half of the second-leg of the semi-final, though. "Depending on what book you read, the crowd at the Bernabeu was anything from 125,000 to 145,000," said Sadler. "The atmosphere was unbelievable. They were the kings of Europe, in all their white splendour, and they had a great team. Gento was getting on, but still a wonderful player. In the first half they murdered us. We were 3-1 down at half-time, and even our one had been an outrageous own goal. We were numb. Even Matt's assistant, Jimmy Murphy, an incredible character who was never short of a word, most of them not in the dictionary, couldn't think of anything to say.
"But I do remember Matt pointing out that we were still only 3-2 down overall, so it wasn't the mountain it seemed. And he made some adjustments. I'd been in a kind of holding position in midfield, but he told me to move up a bit." In the second half, United came out fighting. And it was Sadler who scored the goal which levelled the aggregate score, before Bill Foulkes, improbably, bagged the overall winner. "I somehow managed to nick it," Sadler told me, with characteristic modesty. "I scarcely remember scoring. But I know the momentum carried me past the goal, and remember thinking that it was as if someone had turned a radio off. One second it was blaring away, the next second there was total silence."
The Nou Camp this week will be less intimidating than the Bernabeu 31 years ago. But the match is in Spain, against formidable opponents. So let's hope a bit of history repeats itself on Wednesday, and that a bit of history is made.