What is the purpose of starting stalls?

In British Flat racing, horses compete over a minimum of five furlongs, a distance that they can cover in less than a minute, so it is imperative, ideally, that all the horses start together, in as straight a line as possible. Consequently, the vast majority of Flat races in Britain are started via numbered starting stalls. Nevertheless, it may surprise you to learn that starting stalls were not introduced in Britain until 1965.

Starting stalls feature an electromechanical release system, operated by a single button which, when pressed by the starter, unlocks the spring-loaded mechanism on the front door of each stall, causing them all to spring open simultaneously. They can horses to become claustrophobic and unruly but, even so, add a level of precision and predictability to the start of a Flat race. Previously, a system of five wires, suspended at head height, was used and, before that, a system of flags, which inevitably led to numerous false starts.