The treble is so rare in English football that when Sir Alex Ferguson addressed his players at Camp Nou ahead of the 1999 Champions League final, he likened it to flying to the moon.
Manchester United had already lifted the Premier League trophy and the FA Cup during the previous 10 days, standing on the verge of becoming the first English team to win all three competitions in the same season. But despite his rousing speech before kickoff, Ferguson realised very quickly that even for an outstanding team, the final game of a gruelling season spent fighting on three fronts was 90 minutes too far.