Ground un-fit to play?
In the opinion of one umpire the ground is fit to play and one umpire disagrees. Is it correct that both umpires must agree for play to start?
Yes, both umpires must agree for the match to start. Umpires are taught to work as a team. In all my years of umpiring I have never experienced a conflict over such a decision between two umpires. However, if the two umpires are not independent of the teams then I could understand such a disagreement.