All-figure dialling was a telephone numbering plan introduced in the United Kingdom starting in 1966 that replaced the traditional system of using initial letters of telephone exchange names as the first part of a telephone number. The change affected subscriber numbers in the cities of Birmingham, Edinburgh, Glasgow, Liverpool, London and Manchester which used the Director telephone system. The transition to all-figure dialling occurred between 1966 and 1970 and was initiated by the General Post Office. It was one of the first in a series of changes in the organisation of British telephone numbers. In most areas the change initially only affected the presentation of area codes, but in six multiple exchange director areas such as the London telephone area, the change required the introduction of new local exchange codes. The period of parallel operation of the old and new systems ended in 1970 with the ANN: All-figure Numbers Now advertising campaign. The changes were required for the continued good operation of the telephone service, but were considered controversial at the time. They occurred because of the increase in subscriber-dialled international calls from countries which used a different mapping of letters to numbers on the rotary dial and because the number of useful exchange mnemonics that were possible under the existing system was being exhausted. The implementation of all-figure dialling and new local exchange codes in director areas allowed changes to be made to routing of calls into and out of these areas. Background In six metropolitan areas around major cities, groups of multiple exchanges operated in a director telephone system. The six cities were Birmingham, Edinburgh, Glasgow, Liverpool, London and Manchester. In these areas the first three digits of the seven digit subscriber number was presented as letters chosen to represent the local exchange within the director area. The letters and numbers corresponded as follows: For example, in the London telephone area a subscriber number on the Wimbledon exchange was presented WIM 1234 and dialled as 946 1234. These local exchange codes (introduced in London in 1927) predated the introduction of STD codes by several decades. The General Post Office issued subscriber trunk dialling (STD) codes for most areas during the late 1950s and early 1960s. The codes allowed subscribers to call other exchanges directly and without the assistance of an operator. To help the public remember the new codes they were represented by a recognisable combination of two