Since 1904 it has been legal requirement to display a vehicle registration mark on a motor vehicle on a road going car or commercial vehicle.
In 1963 a standard registration number had the registration year letter on the right -
YUF 612A and registration (number) plates were black with either white or silver letters. At the end of the 1960s number plates became white reflective (front) and yellow reflective (rear) with either pressed or separate plastic letters. Yellow and white number plates became standard in 1973.
In August 1962, number plates were standardised with a national scheme to avoid the problem of registrations running out. An "A" suffix was issued for 1963, "B" for 1964, and so on each year with a new letter of the alphabet, with the exception of the letter "I" and "O" and "Q" and "Z" as these were too easily confused with numbers, "U" was not issued ether. Initially the year letter changed on the 1 January each year.
However, the year letter changing on 1 January each year meant that car dealerships had to register vehicles with the new registration over the Christmas holiday period, and so the system was changed, so that the new year letter came in on 1 August rather than 1 January. This was done in 1967, when "E" suffixes ran only from 1 January to 31 July, before "F" suffixes started on 1 August. New registrations then ran for 12 months, from
August to the end of the following July.
In August 1983 they year letter moved to the left of the number - A 475 VLM. Number plates were by then PVC with only the font of the number being different to today's registration plates.
The changes in 1983 also brought the letter Q into use. The letter Q had never previously been issued as a year letter. It was used on vehicles of indeterminate age, such as vehicles made from kits, substantial rebuilds, or imported vehicles where the age of the vehicle couldn't be proved. The Q registration was also given to vehicles that had been stolen and recovered, but in the meantime had illegally been given a false identity.
Since 1979, cars operated by foreign embassies, consular staff, and various international organisations have been given number plates with the format of three numbers, one letter, three numbers. The letter is D for diplomats or X for non-diplomatic staff.