The race begins at the downstream end of Temple Island, where the crews attach to a pair of pontoons. The race umpire will then call out the names of the two crews and start them when they are both straight and ready. Each crew is assigned to row on either the 'Bucks' (Buckinghamshire) or 'Berks' (Berkshire) side of the race course. The coxswains or steersmen are expected to keep their crew on the allocated side of the course at all times during the race, else they risk disqualification. The only exception is when a crew leads by a sizeable margin and is not deemed by the umpire to be impeding the trailing crew.