There are still many old telephone numbers dotted around London on old signs that show theold exchanges to denote the area code. For example HOL = Holborn, EUS = Euston.
This system lasted until approximately 1966.
See the full list here: www.rhaworth.myby.co.uk/phreak/tenp_01.htm
!["Keep your name in front" - London Transport advertising services folder - exterior - designed by Zero [Hans Schelger] - 1938](http://farm6.staticflickr.com/5021/5616739136_fae6607a93_m.jpg)
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