Willie Collum, has explained what he found difficult about refereeing Glasgow Derby games between Celtic and Rangers. Now retired from match officiating and taking on the role of the SFA Head of Referees, Collum has been in the headlines over the last 24 hours after announcing a new monthly SFA podcast called The VAR Review. The program will allow Collum to publicly discuss VAR decisions made, rightly or wrongly, by his officials and offer clarity on how the match-appointed officials come to their decisions. No longer a whistler, Collum was asked what it’s like to referee a game between Celtic…