Letters for digits in UK telephone numbers

London exchange names
London call office notice 1963
London dialling code booklet 1964
London dialling code booklet 1968
Other UK director exchange names
UK STD codes
UK Telephone Charge Groups with map
An introduction to UK local dialling codes
Archive of various telephone documents
Photo gallery and note re Tardis
Various musings and a few user comments
London Postal Districts (note)  

The Director Cities

When automatic exchanges were introduced in the UK, subscribers in six cities (see table) were given seven digit telephone numbers. These were written as three letters and four digits. One of the most famous was the number for the Metropolitan Police: WHItehall 1212 ie. 944 1212. (See the layout of the UK telephone dial.)

The three letters were handled by a piece of equipment called a Director which translated them into the required routing digits to establish the call. So these cities were referred to as the Director Cities.

In many cases one physical exchange would handle more than one 'exchange' code. Eg. CROydon, MUNicipal and later 681 and 680 were all served from the exchange in Scarbrook Road.

About 1966 the letters were abandoned in favour of all digit numbers because:

  • Certainly in London, they were running out of codes which could be made into meaningful names. (I suppose you could have stretched 688 to be MUVver but what could you do with 555?)
  • International dialling demanded digits only. At that time for overseas operators rather than subscribers.
  • (I think) Even in the UK, away from the Director Cities, phones did not have letters on their dials.

The opportunity was taken to re-organise the exchange codes on a geographic basis. In London, the first two digits indicated one of eight switching centres. Using two digits enabled more exchanges to be kept on their original codes. Eg. all 01-68x's were in the South sector. In the other Director Cities the first digit of the exchange code indicated the sector.

This meant that there was consistency in that in a full national number the three digits after the zero always gave the charging information and always (with a few local exceptions) gave the routing information.


The Director Cities

071London (Inner)
081London (Outer)
091Tyne and Wear

Note how the initial letters of the five cities other than London happened to map neatly on to the middle digits of their codes. Thus Glasgow could have been 0G1. But the codes were never published using letters.

Edinburgh was not really large enough to be a Director City but it was included to make the above mapping work! And because it is the capital.

The 091 code was created about 1990 for an amalgamation of three charge groups in the North East of England. We could retro-fit the 9 on to Wearside, Washington (County Durham) or tYneside.

The UK dial
The letters on UK telephone dials were:

1 no letters
6MN but not O
7PRS but not Q
9WXY but not Z
Apparently people were supposed to be able to distinguish letter I from digit 1 but could not tell letter O from digit zero.

Subscriber Trunk Dialling

Subscriber Trunk Dialling (STD), known in the USA as Direct Distance Dialing (DDD) was introduced in the UK in the early 1960's. The dialling codes for the non-Director exchanges were written as: zero, two letters with mnemonic significance followed by one, two or three digits. Eg.:

0BR2 Bristol
0BR5 6 Keynsham (Bristol)
0SH3 78Halfway House (Shrewsbury)

The use of letters was dropped within a few years but in this case there were no actual code changes except that a few codes which had been put on 0Oxx were changed to leave 00 free for other things (eventually International dialling). Eg. 0OX2 Oxford became 0865.

List of STD codes

London Postal Districts

I first put a link to my list of London Postal Districts in here simply because I could not think of anywhere else to put it. Incredibly, it was weeks later before I thought of a very good reason: the Postal Districts look higgledy-piggledy on the map, for example SE10 is Greenwich and SE11 is Kennington - miles away. And the explanation is the same as for STD codes, Director exchanges and the Charge Groups list - the use of letters.  The Postal District numbers are in alphabetical order. (Back to Contents)



Any comments on this page will be gratefully received by: Phreak@RHaworth.net

Roger W. Haworth   (sgertrow)
1999 Dec 05  First version
2004 Dec 16  First revision in five years
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