This is a list of country codes on UK issued diplomatic vehicle registration plates, i.e. the first group of three numbers. Since 1979, motor vehicles operated by foreign embassies, high commissions, consulates and international organisations have been issued unique vehicle registration marks with a distinguishing format of three numbers, space, letter D or X, space and three numbers. The letter D is predominantly used for vehicles operated in or around the capital of London with the letter X allocated to vehicles outside London and for international organisations, unless otherwise specified by bilateral treaty or arrangement.