Greater Manchester Police estimates that 150,000 fans were in Manchester city centre for United's triumphant homecoming according to this report from 27 May 1999.
At least another quarter of a million people lined the streets along the rest of the route.
In Barcelona the previous evening Manchester United scored twice in injury time for a 2-1 victory against Bayern Munich to win the Champions League Final. In doing so they achieved the treble of Premiership, FA Cup and the Champions League.
Brian O'Connell reports from Manchester where he spoke to some of the fans.
An RTÉ News report broadcast on 27 May 1999.