"A postilion or postillion guides a horse-drawn coach or post chaise 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 (mail) or a messenger, it became transferred to the actual mail carrier or messenger and also to a person who rides a (hired) 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." - (en.wikipedia.org 17.12.2019)
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