G.P.O. / BT Defence Network Organisation

G.P.O. / BT War Organisation (BTWO)

I am most grateful to Dave McKay G1JWG ( www.radiohistory.uk ) for his help in highlighting this subject matter, which he spotted in the contents of declassified Cabinet Office file CAB134-5766, held in The National Archives at Kew.
Extracts from a Home Office report dated 25th May 1993 to be considered at a Cabinet Office meeting on 10th June 1993.
14. The BTWO which would have been dispersed to protected sites, was intended to facilitate BT's restoration of damaged communications in time of war. It was interlinked by their bespoke communications system, the BT Defence Network (BTDN). The GREC recommended that the BTWO be maintained, and its size and arrangements reviewed. A review was initiated by the PRWP in 1989, but suspended pending the outcome of BT's Project Sovereign re-organisation. A joint BT/Home Office working group was then set up by the PRWP in early 1991 to carry forward the review.
15. Once again, the changed political climate and diminished threat of nuclear war were major factors taken into account by this review. Other significant considerations were: the enhancement of the ECN and closure of the EMSS, BBR and AUG; the updated requirements of other Departments; the absence of comparable facilities for other essential services; and the high cost of modernising the BTDN. In July 1992 the PRWP accepted the Home Office's conclusion that the BTWO should be considerably reduced in size to a central core, but that BT's designated wartime Network Management Centre at Oswestry should be retained. The closure process is continuing, and the BTDN was shut on 28 February 1993. The Home Office will pay for the cost of BT's connection to the ECN.

Abbreviations Used

ECN The government Emergency Communications Network, a voice network, during the Cold War period linking Regional Government HQ, Local Authority Emergency Centres (LAEC) and UKWMO group and Sectors. Post Cold War, an enhanced ECN was extended to link together many other user groups, after the closure of the RGHQ and UKWMO sections. Whilst retaining the LAEC. This is described in more detail on its own page; use Page Menu to select Core Communications Networks - Second Generation.
EMSS, BBR and AUG All operated by BT. Each of these topics have a page of their own. Please select from the Page Menu; Post Attack Plans - EMSS | National Communications - Microwave Backbone (BBR) | National Communications - All Underground (AUG).
GREC Government Review of Emergency Communications.
PRWP Post Review Working Party - implementing the GREC Review.
In the above context, all references to British Telecom (BT) also include its predecessors the G.P.O. and Post Office Telephones.

BT Defence Network

The BT Defence Network (BTDN) linked together important operational buildings, such as larger telephone exchanges, repeater stations and microwave radio stations. It linked in the wartime management structure of Area War Groups (AWG) and Regional War Groups (RWG). When post-privatisation reorganisations removed the regional tier of BT's peacetime management structure, the RWG were replaced with a number of control centres around the country. Two have been identified so far, Evesham and Skipton, but there must have been a number of other centres.
There are BTDN circuits marked 'XX SEC' where the 'XX' is an exchange engineering code (1141 Code), the purpose of these are unknown. The best guess is they are telephones in the doorkeeper's security lodge at these larger exchanges, assuming that SEC is the abbreviation for security.
Some parts of the BTDN shared the same switchboards as the EMSS, for example Leicester, Northampton, Oxford and Peterborough. In other towns the BTDN switchboard was completely separate either located in nearby rooms or in completely different buildings. For example at Chester and Worcester in separate buildings.
BTDN on EMSS Switchboard
switchboard jacks
The Cabinet Office file refers to the BT Wartime Network Management Centre at Oswestry, this is co-located with the Network Operations Centre as it was known then. Located at Park Hall, Whittington, SY11 4TB Lat / Lon 52.871399, -3.030835


Although I have been aware of the PODN / BTDN since the seventies, it was not until March 2019 that I discovered it was Government funded and not merely part of the company's internal communications, which would be outside the scope of this website. Hence I have accumulated very little information on this topic.
Feedback via the website Home Page would be most welcome.