According to the Royal Central:
On March 27th 2014, Queen Elizabeth II and the Duke of Edinburgh attended a reception in the City of London to mark the 800th anniversary of the Royal Watermen.
When the Royal Watermen came into being in the reign of King John, the river was a busting highway and the lifeblood of London. It stayed that way for most of the eight centuries the company has existed.
The Royal Watermen can be spotted in their scarlet livery on other major occasions, like royal weddings, riding as boxmen on carriages. And all for the token payment of £3.50 a year.
To read the entire article on Royal Central, please click here.