The Yorkshire Grey was breed of horse favoured by medieval knights for its load carrying capacity, a very important feature when armour got so heavy they had to be craned into the saddle.
In the 18th century the Yorkshire Grey was adopted by the stage coach companies as the preferred engine, which explains the number of pubs with that name on the old trunk routes.
So the rather Charge-of-the-Light-Brigade cavalryman that rides on the roof of the Yorkshire Grey in Holborn, built in 1877, is slightly confusing - such a heavy horse was not particularly in demand at that period. Perhaps the carver (said to have been William Plows) thought that a military man would have more popular appeal than a public transport hack.
If he thought that, he was wrong. The figure has been described as 'an inflated tin soldier on horseback'.