Rangers vs Celtic has been delayed following huge pyro displays from both sets of fans. 

Referee Don Robertson was forced to halt kick-off as smoke filled the Hampden Park skyline. 

Robertson was called in late to referee the clash after Willie Collum was injured during the warm-up. 

The whistler was set to take charge of the powderkeg fixture but has pulled out right before kick-off due to a calf strain.

Daniel McFarlane and Dougie Potter are the assistant referees for the match with Steven McLean in the VAR room alongside Frank Connor.