In reply to a post by witchunt:

They go back decades , possibly before BT plc.
FYI, there are 6 that cover London , 3 for inner , City of London(CL), West End (WE)and Westminster (WR), and 3 for outer , London North(LN) London West (LW)and London South(LS)

They are\were the old 'districts' as they were called then and a CSS for each of them.

The LN coded exchanges extend quite far to the North of London, Hatfield is included

Think it was part of the London charging area, extends to St Albans and Welwyn Garden City.

I never did get a map of all the BT districts across the UK, would have been interesting to see how it was divided up.

dect

There were 29 in total, they are the first two digits of the 5 digit exchange code.

Maps were obtainable from the Drawing office and we used to have them in the office they included all the exchange names and areas on the detailed ones for each region.

My memory says there was something odd about TH, Thamesway, it could have either East Anglia or South East

Scotland: NS, WS, ES.
Wales: WN, SW.
S.West. SS, WW,
N East: NE, MY, SL
N West: LC, LV, MR.
Midlands: CM, EM, WM
East Anglia; EA, SM, TH
S East; ND, SD, ST,
London; CL, LN, LS, LW, WE, WR
N, Ireland; NI

In reply to a post by kitcat:

My memory says there was something odd about TH, Thamesway, it could have either East Anglia or South East

TH is in the South East, as my exchange and the ones around me are all TH….

E.g
https://availability.samknows.com/broadband/exchange...

It was actually Thameswey covered Guildford, Aldershot, Farnborough, Camberley

MHC

Covered right across to beyond Reading/Newbury towards Swindon.

In reply to a post by kitcat:

There were 29 in total, they are the first two digits of the 5 digit exchange code.

Maps were obtainable from the Drawing office and we used to have them in the office they included all the exchange names and areas on the detailed ones for each region.

My memory says there was something odd about TH, Thamesway, it could have either East Anglia or South East

Scotland: NS, WS, ES.
Wales: WN, SW.
S.West. SS, WW,
N East: NE, MY, SL
N West: LC, LV, MR.
Midlands: CM, EM, WM
East Anglia; EA, SM, TH
S East; ND, SD, ST,
London; CL, LN, LS, LW, WE, WR
N, Ireland; NI

Didn't realise there were 29 so thank you for listing them all, only ever managed to have involvement with 5 of them over my time in the job.

Thameswey ….. I’d always thought the weird spelling was based on two lei era in it
Thames and Wey

Around the top end of the M4 and M3, kinda.