SURPRISINGLY, only eight teams have managed to win a comparable trio of competitions, although many have gone close. Some of this select group have been built around outstanding individuals, such as Lionel Messi and Ajax’s Johan Cruyff, while others – like Celtic in 1967 –  were founded on the team ethic. Inevitable comparisons will be made about “who is the greatest?”, but it’s an impossible exercise. A team can only beat the opposition in front of it and in all cases, the treble winners have done just that. This season, only two teams, Bayern Munich and Paris Saint-Germain could join this illustrious list. Celtic 1967 Jock Stein’s team actually won five cups in 1966-67: the European Cup; the Scottish League; the Scottish League Cup;…