Extracts from a Home Office report dated 25th May 1993 to be considered at a Cabinet Office meeting on 10th June 1993. Revealed within the contents of declassified Cabinet Office file CAB134-5766, held in The National Archives at Kew. Paragraph 14 briefly describes the department's purpose.
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 Emergency Communications Network, a government voice network, during the Cold War period linking Regional Government HQ, Local Authority Emergency Centres (LAEC) and UKWMO Groups and Sectors. Post Cold War, after the closure of the RGHQ and UKWMO sections, an enhanced ECN was extended to link together the LAEC with many other user groups. The ECN is described in more detail on its own page, linked from the bottom of this page or found in the A-Z Index in the top of page menu bar.
GREC Government Review of Emergency Communications.
PRWP Post Review Working Party - implementing the GREC Review.
The next three abbreviations are systems operated by BT, each has a subject page of their own on this website.
EMSS The Emergency Manual Switching System
AUG The All Underground Network
BBR Backbone Radio part of the GPO/BT Long Haul Microwave Network
The three pages are linked from the bottom of this page or the topic may be found using the top of page index bar.
Project Sovereign A major structural reorganisation of BT which included loss of staff through voluntary redundancy.
G.P.O. / BT Structure
G.P.O. Telephones, up to and for a number of years beyond privatisation, was organised with Telephone Headquarters in London setting the company policy and budgets. The country was further divided into Regions who were responsible for their part of the budget and exchange and lineplant planning. Each Region was further subdivided into Areas. Each of these areas had a 'Telephone Manager' to who the various departments were accountable. The majority of these departments were located in a 'Telephone Managers Office' a large building or collection of buildings housing hundreds of staff. The map below shows the Area boundaries and the location of both Area and Regional Headquarters.
Telephone Areas within Regions
The Post Office War Organisation (POWO) was organised to reflect these Regional and Area boundaries. A national emergency centre was located in Oswestry coordinating the response.
Post Office telephones was privatised in August 1984 and the POWO became the British Telecom War Organisation (BTWO) In the years after privatisation, during the 1980s there were frequent structural changes. Regions were abolished and areas amalgamated to create Districts. Later those combined to form larger districts almost the same size as Regions had been, but without the bloat of a regional organisation between them and headquarters. Fearing the Government would split the company into smaller units, some departments moved into a 'National Networks' organisation (NN) and the remainder in 'Local Communications' sector (LCS).
The communications network to support the POWO was known as the Post Office Defence Network (PODN) becoming the British Telecom Defence Network (BTDN) after privatisation.
The BTDN at the time of its closure in the nineties contained a mishmash of various circuit markings on switchboards reflecting the original PODN and the various company reorganisations during its life as BTDN. This makes identifying the underlying structure difficult for the researcher. The BTDN also contained a telegraph network enabling hard copy messages to be sent to BTWO locations all over the country.
Area War Group
Reflecting the GPO's Regional and Area structure when the war organisation and its communications network were established in the nineteen sixties, each telephone area had an Area War Group (AWG). This was responsible for co-ordination within its area and liaison with Emergency Service customers. One role was to draw up a list of lines with enhanced telephone service preference, known as 'Preference Category I' and 'Preference Category II' and supply this to the Engineering staff to ensure customers lines terminated on the appropriate type of exchange equipment.
GPO/BT Telephone lines have three categories of preference. Ordinary domestic and most business customers are Category III. Important (to the functioning of the state) business lines and Public Telephone Boxes are Category II. Important customers such as Police, Fire and Ambulance stations, Hospitals, Civil Defence and Military have a Category I status. Introducing category two, prevents category three customers from making calls. Introducing category one, additionally prevents category two from originating calls. All three categories can receive calls.
Communications
The switchboard at a stand-alone AWG is the common type of office / factory switchboard. Known within GPO/BT as a 'Switchboard N1070' this was modified to diagram number SA2054 for use in small EMSS exchanges and here in an AWG. This was superceded by 'Switchboard AT3796' almost identical in appearance to the untrained eye. This type of switchboard although designed in 1935 was still being installed in customers premises in the early nineteen seventies.
AWG Telephone Switchboard and Interface Circuits
Typically the AWG switchboard would have a small group of ex-directory telephone lines, lines to adjacent Telephone Area's AWG, A Trunk Subscriber (TkSub) to the EMSS and Private Wires (PW) or Emergency Circuits (EC) to its Regional BTDN command centre. An emergency circuit is a private circuit that is switched through in an emergency or war situation, but in peacetime carries normal calls from the general public between exchanges.
As well as telephonic communications, the AWG had access to the public TELEX system and a private BTDN Telegraph network for exchanging typed messages. In this photograph the left hand teleprinter is on the TELEX network and the other on the BTDN system.
AWG Teleprinters
The two devices here are the British Telecom Cheetah, known as a 'Teleprinter 87C' and probably having 32 kilobytes of memory for composing messages. Introduced in the early eighties, the Cheetah's life was short lived due to the influx of personal computers and email. The BT public TELEX Network was finally closed in March 2008.
The Defence Network
The Post Office Defence Network renamed the BT Defence Network (BTDN) used manual switchboards to link important operational buildings, such as larger telephone exchanges, repeater stations and microwave radio stations with coordination points 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.
At the majority of sites a suite of switchboards would serve both the Emergency Manual Switching System EMSS and the BTDN. In other towns the BTDN switchboard was completely separate either located in nearby rooms or in completely different buildings, such as Chester and Worcester.
The BTDN part of the combined switchboard generally has very few circuits. One circuit to its own AWG and maybe other nearby AWG too. Circuits marked 'XX SEC' where the 'XX' is an exchange traffic division code for the location of the Subordinate Engineering Control (SEC). The SEC was a localised engineering control for the Public Switched Telephone Network (PSTN) plus any government facilities. Beneath each SEC was a group of MEPs or Minor Engineering Points, where small teams of engineers would be stationed to carry out any actual maintenance work. Sometimes the BTDN switchboard has circuits to important Telephone Repeater Stations (TRS) and automatic exchange fault coordination points.
At a combined BTDN and EMSS, the BTDN circuits are not used for connecting customers, but the EMSS circuits may be used to connect BTDN services through to departments in other parts of the country.
BTDN on EMSS Switchboard
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
War Emergency Procedure
Alex, a non-BT person discovered a wall chart in what he thought was a secret bunker at Abergavenny telephone exchange, this is reproduced below. Abergavenny along with all large exchanges built post-WWII have protected accommodation in their basement which might seem like a bunker to the uninitiated.
Abergavenny is thought to have once been the wartime command centre for the telephone region. The chart refers to BT Instruction numbers, but those are not to hand. Unfortunately some actions make little sense without seeing the details they refer too in the instruction.
Instruction Number
Action
Notes
EM 001
Review plans
EM 111-2
Designate staff
Review transport
Review essential records
Review access arrangements
Finalise Instructions
EM 112-1
Alert advance staff
Prepare passes
EM 113-1
Alert EM Staff for ZHQ
10
Confirm transport
Despatch advanced staff
Alert common services
Alert EMSS Staff
4
BTDN Ready
1
Provide funds
EM 114-2
Despatch common services
Erect F.O.P.
Engineering Stores (BTDN)
1
Alert Main Staff
Despatch EM Staff to ZHQ
10
Provide transport
Man BTDN
1
Advise BTHQ
2
Despatch main staff and records
Despatch ZHQ Staff
10
Advise BTHQ
2
EM 116
Issue instructions
EM 131
Review non-essential work
Review essential supplies
Review dispersal
Review leave
EM 134
Cease training
Cease planning
Confine maintenance
Disperse supplies
Top-up fuel
Cancel leave
Advise BTHQ
2
Instruction Number
Action
Notes
EM 135-2
Requisition
EM 27
Provide Comms
EM 803
Prepare staffing schedule
Alert staff
EM 805
Switch ECs
9
Provide Staff
Review access arrangements
Finalise instructions
EM 811-2
Review KPs and Protect
6
EM 812-1
Complete protection
EM 831-1
Review RADIAC
8
Designate BTLOs
EM 832-1
Alert BTLOs
3
Collect RADIAC
8
EM 835-1
Despatch BTLOs
3
Distribute RADIAC
8
Advise BTHQ
2
EM 852-2
Control News Releases
EM 862
Switch BBC ECs
9
EM 871
Review plans
EM 874-1
Erect F.O.P.
5
Make EMSS Ready
4
Confirm staff alerted
Introduce PREF CAT II.
7
Prepare for PREF CAT I.
Advise BTHQ
EM 874-2
Prepare LR
EM 875
Activate EMSS
4
Introduce PREF CAT I.
7
Advise BTHQ
2
EM 876
Activate LR
Advise BTHQ
2
Author's notes
These do not form part of the wall chart, but added to explain some details. The use of BT implies its predecessor the Post Office / G.P.O. too.
BTDN BT Defence Network, telecoms to support the work of the BT War Organisation in the event of the normal public network failing.
BTHQ British Telecom war headquarters.
BTLO BT Liaison Officer. An engineer embedded within a UKWMO, regional government or council bunker to maintain its communications systems.
EMSS Emergency Manual Switching System, a skeleton manually operated telephone system supporting the military and civil defence organisations. This is described in it own chapter found in the Chapter Index on the page menu bar.
F.O.P. Fall Out Protection, special protection often in the form of dry interlocking construction blocks used to create a wall, to shield staff from the radiation given off by nuclear fallout.
KP Key Point, important parts of the telecoms network requiring protection from sabotage during the period of tension. Protection provided by the police and military.
PREF CAT abbreviation commonly used for Preference Category. The three categories are explained in the Area War Group topic.
RADIAC Devices for measuring the radiation levels after a nuclear attack to see where was safe to go when clearing faults or attending work.
Switch EC, Emergency Circuits (EC) are normal lines between exchanges during peacetime carrying our calls around the country. At times of war and exercises these lines are switched to create private circuits for special services. Prior to the nineteen eighties communications modernisation, the UKWMO relied heavily on ECs. The BBC ECs, would carry special War Time Broadcasting Service programs to their transmitters all over the country from a central underground studio at Wood Norton, Worcs.
ZHQ Zone Headquarters, formerly known as RSoG (Regional Seat of Government) or RSG and RGHQ (Regional Government HQ) At times of war, GPO/BT Engineering Maintenance (EM) staff would be stationed within the ZHQ buildings to maintain and clear faults on telecoms equipment.
Staffing in an Emergency or War
During a civil emergency or war it would be necessary for staff to be based at key points within the telephone network infrastructure. These may be important exchanges, repeater stations, radio stations and EMSS / BTDN locations. The welfare of the staff must be considered by providing meals, sleeping, washing and toilet facilities.
Ration boxes for the switchboard operators and engineering staff were stored on site even during peacetime. The examples below can be dated by the British Telecom dotted 'T' logo to between 1981-1991 when it was replaced by the piper symbol. By then the cold war had ended and EMSS wound down, its unlikely there were any rations carrying the piper logo.
BT Single Person Ration Boxes in Storage
Emergency locations were often situated in below ground sections of a building where possible. Many key locations were totally above ground such as repeater or radio stations which offered little or no protection from the radiation given off by nuclear fall-out. Even basement locations may not give sufficient protection.
In order to create radiation protection for staff at these locations, the Ministry of Public Building and Works designed interlocking high density concrete blocks, that could be assembled by untrained staff without the need for mortar. Walls or enclosed spaces could be created or window openings blocked. The density of the nine inches of concrete gave the required level of protection.
Plans were drawn up showing how the blocks were to be assembled, floors marked with paint and the required number of blocks stored on site so they could be moved into place should the need arise.
Fallout Blocks in Storage
The blocks are very cleverly designed to interlock both horizontally and vertically, for added stability the E-Type block can be rotated vertically and interlocked. The nose of the chevron is flattened to allow the blocks to better mesh together. The majority of the wall is constructed with 'E' type blocks, but other designs the K-Type & L-Type create corners. The A-Type design has a flat bottom to spread the load when laid directly on a floor. If a protective 'roof' is required, blocks with flat tops allow planks to be laid across two parallel walls to support concrete slabs.
The Shape of the E-Type Fallout Block
The photograph below shows a safe area constructed within an important microwave radio station on the Backbone (BBR) network. The structure is 2.2 metres (7ft 4in) tall. As radiation travels in a straight line from radioactive fallout on the ground outside this is sufficient to protect an occupant while standing inside the refuge. It should be stressed the block wall offers no protection against bomb blast.
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