Ron Atkinson remembers it as more of a screech than a roar. 'I've never heard anything like it at any other football ground,' Big Ron, now 83, told Sportsmail this week.
For Bryan Robson, his captain that night, it is still the best atmosphere he has experienced at Old Trafford.
'The fans had even climbed the floodlights to get a view,' says Robson. 'I managed to score early on and the noise was so loud it felt like the pitch was shaking.'
Young substitute Mark Hughes, in whose career Manchester United and Barcelona would play such an important part, came on for the last 20 minutes to help defend a three-goal lead as Atkinson's side won 3-2 on aggregate in the quarter-final of the UEFA Cup-Winners' Cup.