Celtic will enter the San Siro this evening firmly in the role of underdogs.

They were, however, even less fancied on that famous May afternoon in Lisbon. In this extract from his authorised biography, the late Sean Fallon remembers how Jock Stein's side confounded all expectations and reduced their manager to tears.

The Inter Milan of 1967 were a side that had won the European Cup twice in the previous three seasons and beaten holders Real Madrid en route to the final. World Soccer magazine previewed the final as a foregone conclusion, with Roger MacDonald writing: "Inter, with their ruthless, relentless tactical system, have reduced uncertainty to a complete insignificance. When Inter win the final..."

MacDonald's misplaced conviction appears foolish in retrospect, but his opinion was shared closer to home. Jim Craig remembers being "floored" by his father telling him that he did not want to travel to Lisbon. "He said he thought Inter would be too strong and did not want to go over and see us beaten," said the full-back.

Sean Fallon wasn't nearly so pessimistic. In a newspaper column in the build-up to the final, he confidently forecast a Celtic victory. He was even bold enough to predict the scoreline.

"I said it then: Celtic will win 2-1," Jock Stein's famous assistant recalled in 'Sean Fallon: Celtic's Iron Man'. "That column got me into trouble though. Jock was raging about it at first. He said I was tempting fate. But I felt confident and thought it was important that we inject some of that into the players. And Jock and I never fell out for long. As the game got nearer, I could see him becoming more and more confident."

What neither Stein nor Fallon could not prepare for in Lisbon was the bus driver taking them in the opposite direction from the stadium. But while there was a suspicion that this mistake might not have been entirely honest, Celtic's late arrival seemed, if anything, to work in their favour.

"I'm sure that helped us," said Fallon. "The players had been singing Celtic songs on the way to keep themselves relaxed and by the time they got ready there was no time to be nervous. What I remember more than anything is the first sight of the stadium, which was beautiful, and then hearing the fans. They said we had three times as many supporters as Inter that day, and they seemed to make 10 times as much noise."

Bertie Auld remembers this support being central to Fallon's pre-match involvement. He said: "The boss (Stein) gave a short speech, just saying: 'You've made history. Now go out there and play to your capabilities.' But after it was finished you knew that Sean would come round and give everyone little individual pep talks. I always remember in Lisbon, he said to me: 'Did you see all those people? Did you hear those songs? Go out and do them proud.'"

And Fallon's psychological work was not yet done. In his autobiography, 'Hail Cesar', Billy McNeill told the story of Helenio Herrera, Inter's revered manager, attempting to snatch Celtic's pre-assigned bench ahead of kick-off. "I recall Sean threatening to 'set about' Herrera if he didn't shift - and Sean was not a man to be messed with," wrote McNeill. "It was a perfect example of confidence-building."

Celtic, of course, had to draw on those reserves of self-assurance inside seven minutes, when Inter took the lead. For those on the bench, the tension became near-unbearable.

"It's easy for the players," said Fallon. "Once they're out on the field, the nerves disappear. I always found that during my own career. But sitting at the side, I couldn't stop myself from shaking. Jock was nervous too; I remember seeing him grinding his fist into his palm. That said, we always believed we would win. We could see the plan was working. By dragging players out of position with good movement, which our forwards had, we were creating space for players that Inter weren't so worried about."

The source of Celtic's equaliser - set up by one full-back, scored by another - confirmed the wisdom in that strategy. From the moment Tommy Gemmell's shot flew in, and with any remaining neutrals in the stadium now firmly behind the Scots, there was only ever going to be one outcome.

The point at which the inevitable became official - the sounding of the final whistle - was captured in a memorable photograph of the Celtic bench. Bob Rooney is leading the charge, but front and centre - springing forward, fist raised in triumph - is Fallon. Conspicuous by his absence is Stein. The last shot of the manager, as the match neared its conclusion, shows him heading towards the dressing rooms, seemingly unable to watch. Yet his assistant saw immediately that it was not the tension of the situation Stein found unbearable. It was the emotion.

"Jock wasn't nervous," explained Fallon. "He was just so proud by that point that he had started to get tearful, and he was embarrassed. He didn't want the players to see him like that so he just got up and walked away. While everyone was celebrating, he was down in the tunnel composing himself. We were great friends, so I always knew there was another side to Jock. But that was something to see even for me, because he wasn't an emotional man in normal circumstances. But that day, it all hit him."

It had been a performance well worthy of Stein's tears. The manager's pre-match pledge - "we want to make neutrals glad we've won it, glad to remember how we did it" - had been fulfilled in some style.

Francois Thebaud, of French magazine Miroir du Football, summed it up thus. "Surely, never in the history of world sport has a team created as many new fans as Celtic, never has a victory been more warmly welcomed, nor a winning goal been greeted with such an explosion of joy throughout the continent." Celtic, national laughing stocks just a couple of years earlier, had become continental revolutionaries.

'Sean Fallon: Celtic's Iron Man' is out now in hardback and ebook from BackPage Press