This is wiki, however it does have some interesting little details about royal cars since the turn of the 20th century.
https://en.m.wikipedia.org/wiki/State_and_royal_cars_of_the_United_Kingdom
‘On the bonnet of each State and Semi-State Cars there is a mount to which a mascot is attached. The mascot used depends on the occupant and the location. Three mascots, which have passed through the family, are frequently seen: St George and the Dragon is seen on the Monarch's car in England; a Lion is seen on the Monarch's car in Scotland; and Britannia is also seen, a mascot used by George V, George VI, Queen Elizabeth The Queen Mother, and Charles III, when he was Prince of Wales. When the car is not on state business, the standard manufacturers' mascot is used.’
Also from Wiki
Like all British state cars, the Bentleys have a mount on the roof for an illuminated coat-of-arms and a pennant, which can be inserted from inside the vehicle. These usually feature the royal coat-of-arms and the Royal Standard respectively, although other symbols can be used for occasions such as a state visit. When carrying the Queen the Bentley "Flying B" bonnet mascot was replaced, either by the Queen's personal mascot of Saint George slaying the dragon made by the artist Edward Seago, or, in Scotland, by a single standing lion. The Bentleys are equipped with flashing blue lights, two within the radiator grille and two mounted on the front bumper. The State Limousines neither have nor require number plates. The Bentleys are painted claret and black, in keeping with all British state vehicles.