In the aftermath of Manchester United's epic victory over Bayern Munich in the 1999 UEFA Champions League final, manager Sir Alex Ferguson declared he could not see any club landing another domestic and European treble.
A dramatic 2-1 win over the German champions in Barcelona gave the Red Devils a Premier League, FA Cup and Champions League triple crown.
Celtic in 1967, Ajax in 1972 and PSV in 1988 had each won a treble by adding the European title to their domestic league and cup double.
So Ferguson obviously would have been alluding to the tougher English scene when he said that United's treble was "a one-off, something that will never be done again".
Barcelona would prove him wrong and snare a La Liga, Copa del Rey and Champions League treble in 2009 and 2016, while Inter emulated the 'Blaugrana' by winning the Serie A, Coppa Italia and Champions League in 2010.
What Ferguson would never have imagined amidst the euphoria of 1999 is that 20 years later United's rare achievement could be surpassed by their closest rivals Manchester City, whose Etihad Stadium is seven kilometres from Old Trafford.
United's neighbours were languishing in the third tier of English football when Roy Keane and his cohorts were rampaging across the battlefields of England and Europe as the 20th century was drawing to a close. But times have changed.
City were a mid-table premiership club that had not won a major trophy in 32 years when they were acquired by Emirati royalty in 2008.
No expense was spared in building a stellar team and a brand new home ground designed to firstly take English football by storm and secondly conquer Europe.
Money was no object for Sheikh Mansour and City were able to obtain the services of some of the finest players and best coaches money can buy.
They would become the modern equivalent of Santiago Bernabeu's Real Madrid in the 1950s.
Since Mansour took over the club, City have won the championship in 2012, 2014 and 2018 after securing the FA Cup in 2011.
They also snared the League Cup in 2014, 2016 and 2018 yet European glory has regularly eluded them.
This season however, could be City's most memorable in their history because Pep Guardiola's super side have found form after a patchy period before Christmas and are seen in some quarters as slight favourites to retain their Premier League title, win the FA Cup and land the elusive Champions League.
They lead the Premier League race by one point over Liverpool (with a better goal difference) and are in the quarter-finals of the cup and in Europe.
City won their first trophy of the season by beating Chelsea on penalties in the League Cup final so a rare quadruple is still on the cards.
They probably are playing the most sophisticated football on the planet and now that superstar Sergio Aguero is on fire and Leroy Sane and Raheem Sterling have taken their game to another level it surely must be only a matter of time before they emulate their crosstown rivals.
City's overall attacking strength was evident in the Champions League round of 16 clash with Schalke 04.
The German side are having a poor season - they are fifth from bottom in the Bundesliga - but nobody would have foreseen City's 7-0 ruthless demolition on top of their first-leg 3-2 victory.
Current form would suggest that City are the team to beat domestically and on the continent.
None of the Champions League's survivors would relish being paired with City when the quarter-final draw is made on Friday night (AEDT).