British numberplates were 100 years old in August 2003.
Initially they comprised of one or two letters followed by up to four numbers.
February 1963 saw the age identifying suffix introduced.
The suffix changed on January 1st until 1967 when it swapped to August 1st
The letters I, O, Q, U and Z weren't used in mainland Britain.
Northern Ireland, however, has used I, Q and Z.
1983 saw the layout change, the year defining letter as the prefix instead of suffix.
V, W, X and Y prefixes were issued at 6 monthly intervals to ease August sales.

September 1st 2001 saw a completely new system introduced
The first two letters identify one of 40 DVLA issuing offices
Then two numbers indicate the age, for example:
March to September 2003 is 03, then the next six months is 53
The last three letters are random, uniquely identifying the vehicle.

The Q prefix, introduced in 1983, is for vehicles like kit cars and imports
Three numbers, letter D, three more numbers are issued to London embassies.
Three numbers, letter X, three more numbers are issued to staff of consulates.