At a successful club like Manchester United, no stone is left unturned in preparing the players for action – and that includes their sun tan.

A fascinating study into the methods of manager Sir Alex Ferguson by academics at the Harvard Business School in Boston has revealed that United had a Vitamin D machine installed for compensate for Manchesters lack of natural sunlight.

United had a vitamin D tanning booth installed in the dressing room at their Carrington training ground so the squad could counterbalance the lack of sunlight.