The practice began with the two colleges racing upstream from Iffley Lock to a finishing line just short of Folly Bridge. Both crews began one behind the other in the lock, with each having to push their way out of the lock before being able to commence racing. This created an inevitable gap between boats, with the one behind trying to bump the one in front to claim victory. The boat in front could claim to be "Head of the River" if they avoided being bumped. As the number of crews contesting races increased, races ceased to start in the lock, and instead were started from the bank upstream of the lock. This first occurred in 1825 or 1826.