His faith in himself was to be neither broken by Benfica nor sapped by the demanding 100,000 crowd as, shirt flapping out of his shorts, he dominated the left flank to wreak confusion in the heart of the Portuguese rearguard.
Even in a team containing Charlton, George Best and Brian Kidd, who all scored in the 4-1 extra-time triumph, it was the callow Mancunian who was, by consensus, the man of the match in United's first European final. It had taken them 12 years to reach it, but now they were the first English club to claim club football's most sacred trophy, the European Cup.
It provoked several debating issues for the pub pundits; notably, Best's impudent deceit of goalkeeper Henrique as he scored one of three United goals in eight minutes that settled matters in the extra half-hour, and United goalkeeper Alex Stepney's thwarting of the omnipresent Eusebio. Yet, according to the Daily Mail's commentator J L Manning: "There was another contest almost as decisive between Aston on the left wing and Adolfo at right-back. No one at Wembley will forget the way Aston played his part. On the day Best came out worse".
It was undeniable that this unassuming young man had eclipsed even the Belfast beau. He possessed a fleetness and sleight of foot that suggested he should have had Martin affixed to his surname. Today, his recollection of his duel with Adolfo is marvellously understated. "The lad was a decent right-back," Aston recalls. "But he had no pace. So I was on a winner from the start."
It was the significance of the moment that has remained with him. "It is one of the few things in my life that never diminishes with time," he says. "I remember the George Best goal, a great Alex Stepney save, and I can remember playing well. But they were all very secondary to what it all meant. It was Matt Busby and Manchester United's greatest night. That's what makes me very proud."
He adds: "When Munich happened, I was 10. I played with lads who were in that crash. My life had doubled by then but, for people like Bill Foulkes and Bobby Charlton, it must have gone by in a flash. I had no idea at the time of the magnitude of what the club, and those players, had achieved, and what it had meant to them."
Aston broke his leg the following season and eventually moved on to Luton, where he enjoyed a profitable five years, before ending his career at Blackburn. Today, Aston is 51, married to Gaynor and has a teacher son, Mark, and a daughter, Faith, training to become one.
Once he regularly got the bird at Old Trafford. Now, he provides seed for them from his three pet shops near his home in Ashton. "I got into it when I was at Old Trafford. In the afternoons it was either the snooker hall or the betting shop, but I decided to learn a trade. My family were in the business and I helped out in the warehouse."
Pet shop man from boot room boy, Aston's immersion in the Manchester United culture was inevitable, given his talent and the fact that his father, also John, was the Old Trafford youth team coach after retiring from a playing career in which he won an FA Cup winner's medal under Busby in 1948.
Last week, the BBC2 programme Reputations, suggested that Sir Matt wasn't exactly the smiling-eyed avuncular figure that is the legend of popular perception. For some disciples of the man whose teams captured five championships and two FA Cups, the broadcast was as sacrilegious as shattering a stained- glass window of Christ. Not necessarily to those who played under him. "I thought it was very accurate," insists Aston. "He came across as a hard-bitten, uncompromising man who had to make some tough decisions. But he was a manager. What do you expect? He was never, to me, a father- figure. I had tremendous problems with the crowd and never once did he offer to help me. But I accepted it.
"That's the way the club was run. It worked on a star system. He got what he considered to be the best players and he put you in the side and you performed, or you didn't. To put it another way, he taught you to swim three or four strokes and then threw you in the deep end. You sank or swam. I was one of those who did several lengths that night at Wembley."
Aston added: "Matt Busby wasn't a tactician; he was a great handler of men, a manipulator of people. People never believe me when I say this, but I never received any coaching. Nobody did. We had a trainer, Jack Crompton, and that's what he was, not a coach. We never worked on tactics, we never practised a throw-in or a corner.
"Matt always believed he'd win and made you believe. He was a very powerful speaker and had a great gravity about him. When he spoke his voice seemed to come from the middle of his chest. He could say `Let's have a cup of tea' and it sounded like an edict from on high."
Aston remains convinced that when the crowd got on his back it was purely the consequence of him being judged by such extraordinarily high standards. "My problem was that I was young and in a team with three genuine world- class players," he maintains. "If you picked a world eleven now, you wouldn't pick three from United, but you'd have picked Law, Best and Charlton then. For me, it was a bit like being a workhorse alongside thoroughbreds. It did get to me, but my reaction was a stiff upper lip. I just used to grit my teeth and say: `To hell with it, let's get on with it'."
Busby made only one exception to his philosophy, George Best. "He made allowances for him because nobody, including the boss, could believe his skill. If you call George a genius, then you don't call anyone else a genius. He was in a class of his own and still is. Ryan Giggs is an outstanding player, and David Beckham has got tremendous qualities; he's a great crosser. But neither approach him as a footballer. George had two great feet, he could dribble, he was good in the air and he could tackle as well."
Yet, for all the mesmerising powers of the man who beguiled defenders as readily as he broke female hearts, Best's increasing dependency on the bottle and his unreliability coincided with decline of the club. Aston had seen it coming even earlier. "There was a strange deflation at the club after reaching that peak of the European Cup," he says. "Nobody knew what to do afterwards. There was no game plan to carry that success on like there is now."
Aston rarely attends games these days, but follows United's fortunes on television. He used to stand on the terraces, pre-Taylor Report days, but disliked the draconian conditions necessitated by crowd violence. "I remember going to a couple of away games and I was shepherded in along with everyone else. I thought: `I'm better than this. I'm not going to be treated like this'."
Nothing will give him greater pleasure than watching Ferguson's United emulate Busby's men. "It's a golden era at the club and, unlike us, I think success will be an ongoing thing. People look at me now, a bald- headed man with a beard and it reminds them just how long it is since they did it. If they win on Wednesday, my feeling will be: `It's about time'."
Just as they were saying at an emotion-dripping Wembley 31 years ago.