Another notable photo-capture of member EU83 is of the short-lived issue to the international settlement of TANGIERS, an enclave in Morocco, facing Gibraltar across the Straits. The plates followed the British style of the times (and might have been made across in Gibraltar, half-an-hour away on the ferry.)
T-4145 is seen here in 1940s London.
(From 1661-4, TANGIERS was a possession of the British Crown.)
An example of a territory which was not party to the treaties permitting free circulation of foreign vehicles, was the TANGIERS international enclave, and to visit Britain after the WW2, this owner was given QC (foreign visitor to Britain) plates to permit his entry. Q-C was allocated to, and handed out by, the the Royal Automobile Association (RAC), as were Q-D and Q-H. The RAC and AA auto clubs assisted travellers with the considerable documentation required for international travel in those times – Motor Insurance, Carnets (partly to prevent the sale of cars in foreign countries), supply of International Ovals (seldom available in the originating countries) and so on.
T 50 & T 11259. Evidence of diplomatic activity in TANGIERS is given by these pictures below, 11259, circa 1953.
The system existed until 1956, when the TANGIERS internationally-administered zone was re-incorporated into the Kingdom of Morocco. You have to be fairly elderly, by now, to have seen one of these in circulation!
Most interesting explanatory notes are given below, by Thierry Baudoin, who studies the Conventions regulating international vehicle movement. (See Comments).