A postilion or postillion guides a horse-drawn coach or post chaise while mounted on the horse or one of a pair of horses. By contrast, a coachman controls the horses from the vehicle itself. Originally the English name for a guide or forerunner for the post or a messenger, it became transferred to the actual mail carrier or messenger and also to a person who rides a post horse. The same persons made themselves available as a less expensive alternative to hiring a coachman, particularly for light, fast vehicles. Postilions draw ceremonial vehicles on occasions of national importance such as state funerals. On the battlefield or on ceremonial occasions postilions have control a coachman cannot exert.
Mount
Postilions ride the left or nearside mount because horses are mounted from the left. With a double team there could be two postilions, one for each pair, or one postilion would ride on the left rear horse in order to control all four horses.
Livery
“The postilion wears a full-dress livery with a short jacket reaching to the waist only and decorated with gold lace and gilt buttons. A white shirt and stock tie, white leather breeches, white gloves, decorated cap, boots with brown tops, and an iron leg-guard on the “leg to protect it from the battering of the carriage pole”.
Purposes
Much cheaper than hiring a coachman.
Privacy for passengers in their conversations.
Special purposes
Better control of the horses, for example, when moving guns at high speed on a battlefield.
Extravagant display by their noble owner for example when attending a state occasion. The display might extend to liveried men walking on foot beside each horse.
Travel by post
This style of travel was known as "posting". The postilions and their horses would be hired from a "postmaster" at a "post house". The carriage would travel from one post house to the next, where the postilions and/or spent horses could be replaced if necessary. In practice unless a return hire was anticipated a postilion of a spent team frequently was also responsible for returning them to the originating post house. Posting was once common both in England and in continental Europe. In addition to a carriage's obvious advantages on long trips it tended to be the most rapid form of passenger travel. Individually mounted riders are subject to their personal endurance limits, while posting could continue indefinitely with brief stops for fresh horses and crew. In England, posting declined once railways became an alternative method of transport, but it remained popular in France and other countries.
To adapt to the rigours of horses traveling long distances at a trot, postillion riders adapted a method of rising and falling with the rhythm of the horse's gait and given the name "posting" or "posting to the trot." "Posting to the trot" is quite different in action from the customary "rising to the trot".