What was Backbone and why is it such an emotive subject?


In specialist circles certain words and phrases can acquire highly charged connotations; they become triggers for heated argument, outpourings or even denial. To the casual observer this degree of emotion seems strange, even bizarre.

One word that has acquired such status is Backbone, a term used to describe a subset of the microwave network established in the 1950s by the Post Office for public telecommunications.

At the outset we must exercise care in the use of the term Backbone, as this may mean different things to different people, depending on whether a capital B is used. In his books [1, 2], Duncan Campbell chose to identify certain key routes as 'the Backbone network', whereas others use the term fairly indiscriminately to cover all or most of the system (which is both misleading and wrong).

Steve Fox, a dedicated researcher, has come across an official reference to the backbone system in government documents. He found this at the Public Record Office (PRO) in a reference to the state of civil defence communications as at 1st Jan 1957.

Attempts to trace official use of this term within publicly available Post Office documents have not met with much more success, and even here 'Backbone' appears to be have a far less specific meaning than that Campbell attributes to it.

One of the first Post Office documents mentioning 'Backbone' is the Post Office Electrical Engineers' Journal of October 1956, which in a section on microwave development (page 223) says:

Microwave Developments

The first use of microwave systems by the Post Office was for the transmission of television programmes; the Sutton Coldfield station of the B.B.C. was initially linked to London by a radio-relay chain in 1949, and the Kirk O'Shotts station has been served by a system from Manchester since 1952.

The first embodiment of a system designed to the new Post Office specifications will be a main radio link between London and Scotland with branches at intermediate points. The main link will carry six broad-band channels in each direction; one or two of the broad-band channels would be for use as a standby.

Following hard on the heels of the above "backbone" system will be the development of radio-relay systems for up to 2,000 telephone channels, or about 1,000 telephone channels together with one television channel.

This article puts forward the impression that the functional justification of the microwave network was to provide the additional bandwidth required for television distribution, the same argument that was advanced to Duncan Campbell when he made enquiries for his articles in the early 1980s. The Post Office could equally well have used coaxial cables for television purposes; the first and second London-Birmingham coaxial cables had both been designed with television in mind and parts of the second L-BM cable are still used to carry television programmes. Whilst microwave links would undoubtedly have given extra capacity, television alone would not have provided an overwhelming argument for establishing new microwave links, particularly over some of the routes constructed as microwave.

There is in fact evidence that the core microwave network was already planned long before the colour TV 'explosion' provided convenient justification, and the real justification was clearly for national defence. Proof can be found in the following documents.

Ministry of Housing & Local Government news release, 15th March 1957.

RADIO STATION TO BE BUILT IN CHILTERN VILLAGE: GOVERNMENT DECISION. The Government have agreed to the siting of a Post Office radio station on land to the west of the London-Fishguard road (A.40) ... near Stokenchurch, Buckinghamshire. [material omitted] The station is required by the Post Office primarily for the purpose of national defence but it will also have civil uses.

Letter to the National Parks Commission from the GPO Buildings & Supplies Branch, 1st June 1956, on file at the Public Record Office:

RADIO STATIONS. I enclose a list of the sites we are seeking to acquire. I should like to take the opportunity of amplifying the answer I gave to one of the questions I was asked at the meeting—as regards the importance of the stations we were discussing for national defence. You may remember I was a little cagey on this point because, frankly, I was waiting for a ruling on the point from the security point of view. I can, however, now say quite definitely that the prime purpose of these stations is connected with national defence and it is for defence reasons that we need to acquire sites as we have proposed.


Cutting from The Times, 19th January 1961 (extract):

The PO, Ministry of Works and Bucks CC were criticized by the Director-General of the Nature Conservancy at the public enquiry over a proposed radio station site in the Chilterns, which ended at High Wycombe yesterday. [much omitted] Mr J Lawrence, appearing for the Postmaster-General, said the radio station would be essential to Britain's defence policy. It would be a key point linking a chain of radio stations in a national network of communications which would be vital in time of attack, when normal landline communications might be destroyed. [rest omitted, not relevant to this].

And finally—

The primary need for this radio station... is to maintain essential defence telephone and telegraph communications. Once established such a station would permit the further development of the normal peacetime network for public trunk and television services (such as 625 line and colour TV)... .All the new stations are in process of development. The Post Office is responsible for ensuring that in the event of an attack on this country adequate communications for the administration of the country are available up to the time of the attack and as far as possible to assist in the work of restoration afterwards.

This last statement was made as part of written testimony given by Mr J. H. H. Merriman, then an engineer and later the Post Office's technology director, when a planning inquiry was held in 1962 over the building of a tower at Wotton-under-Edge, near Stroud in Gloucestershire (cited by Duncan Campbell in his book War Plan UK).

These documents make it pretty clear that the expansion of 625-line television was no more than a cover story and that defence applications were the prime raison d'Ítre of Backbone (as Campbell argues in one of his New Statesman paperbacks [2]). When Backbone was first built, 625-line television was not even at planning stage and colour television (on 405 lines) was purely an experimental exercise that did not mature into a public service until 1967. In [1] Campbell states that extensive plans for a 'survivable' communications system were made during the 1950s and that the backbone microwave system was nearing completion already in 1960. His extensive description of the Backbone system notes that its first leg was constructed along the route London-Birmingham-Manchester-Leeds, followed by bypasses (alternative routes) for these four main cities and two new hubs for 'emergency links'.

What he calls the Northern backbone system was built in 1962, staring from 'the second new hub of the emergency network, the Hunter's Stones tower near Harrogate'. This section of the network ran to Dundee, with a subsequent bypass around the Tyneside conurbation by way of Muggleswick. He lists a number of spurs off the Backbone network and concludes by stating the whole system was designed explicitly for use under conditions of nuclear war, save its use in peacetime for providing eavesdropping 'sigint' (signals intelligence) links to the US National Security Agency base at Menwith Hill, near the Hunters Stones tower.

It is worth noting that the main expansion of the microwave network occurred in the late 1950s and therefore had nothing to do with the main burst of ROTOR installation, which was complete by 1953-55. It is thus wrong to justify the microwave network on the basis of early ROTOR, a project that was defunct and well into revisions by 1957-58. In any case, ROTOR had no need for wideband transmission links; its communication requirements were remarkably 'low-tech', using merely teleprinters and telephones. There is no mention of relaying radar (in effect, video) displays from outlying radar stations to central controls. In fact the original ROTOR scheme was just 1945-style radar defence relived on a much bigger scale and complexity but still using the latest version of World War II equipment (until T80 came on-stream in 1954, at which time everything looked very different and the pace of change started to hot up). Large-scale video and data transfer came with T80 (in part) but much more in the 1958 scheme and with PLAN AHEAD/LINESMAN.

Lay observers sometime overlook the fact that even the highest priority schemes are bound by budget constraints and what can feasibly be manufactured and installed within a given timeframe. Constructing defence or 'emergency' communication systems for use exclusively in time of threat is a luxury that few governments can afford, certainly not the British government in the Cold War period.

Accordingly the notion that vast communications facilities were build exclusively for emergency use is mistaken. It is more realistic to see envisage defence as the prime justification for new works that were then constructed for civil use but in a way that facilities could be pre-empted at short notice for defence purposes. The route taken by such cables and microwave circuits would be optimised to serve both civil and defence installations as conveniently as possible. Conspiracy theorists will always be able to find proof for their outlandish ideas but the truth is usually (not always!) more prosaic.


Emphasis in bold is by the author. Thanks to Mark Bennett and Steve Fox for inspiration and help with this article.

Reference 1. War Plan UK: The Truth about Civil Defence in Britain. Burnett Books, 1982.

Reference 2. Big Brother is Listening: Phone Tappers and the Security State. NS Report 2, published by the New Statesman, 1981.

A simplified plan of BT's UK microwave network with Backbone shown in bold is given in Duncan Campbell's book War Plan UK.



Subsequent research shows that the term 'Backbone' predates all this by many decades! Post Office circular E.12, dated 1909, uses the term 'backbone trunk telephone circuits' in paragraph 164. it is clear then that the expression has a long pedigree!



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