Backbone- the Cold War Secret Communications System

In 1956 a General Post Office document was written to propose a purpose built national communications system that could withstand a nuclear attack on Britain. The paper was classified ‘Top Secret’ and can be seen in its entirety on the website of the government’s National Archives (see link at the bottom of the page).

In the 1950s it was realized that the normal telephone cables that run through the major cities would be very vulnerable to nuclear bomb attack. Such a strike would also make radio communication difficult - the radioactive fallout would interfere with the broadcasts. However, microwave radio signals would not be affected, and so a plan was hatched to place a series of microwave transmitters and receivers throughout the country, and link them together. This was to be called ‘Backbone’, and it would play a crucial response to a nuclear strike in the following ways:

Firstly it was an early warning system of an imminent strike. Secondly, it would be used to coordinate defence during an incoming enemy aircraft attack (the earliest nuclear bombs were dropped by plane). Thirdly it would be used to direct orders to the RAF for a counter attack against the Soviet countries.  Finally after the detonation the civilian and military emergency response would be coordinated using the system, and it would also be used to  communicate with allies overseas.

The initial network was 14 purpose built towers that could communicate from the South of England up into Scotland. Other important military and civilian sites would later feed into this system.

Each tower had to be within view of the last one, as microwaves don’t travel well through obstructions. The original system ran as a line-of-sight from the South to North as follows:

Tring (Hertfordshire) , Charwelton (Northamptonshire)  ,

Pye Green (Staffordshire),Sutton Common(Staffordshire),

Saddleworth (variously in West Yorkshire, Lancashire, Greater Manchester), Hunter Stones (Skipton, North Yorkshire) , Azerley (Yorkshire), Richmond (Yorkshire),

Muggleswick (County Durham), Cold Fell  (Cumberland/Cumbria), Lockerbie (Dumfries), Green Lowther (Dumfries), Kirk O’ Shotts (Lanarkshire)                            

Backbone Sites within the Lancashire Region -

Saddleworth

The original Backbone site in our region was the one at Saddleworth. This can still be seen today. The tower can clearly be viewed when driving away from Halifax towards Manchester on the M62. It is on the left hand side of the motorway, standing high on the moor just after junction 22. The site is still in use for as a mobile phone mast. You can view some pictures of the tower on the website of LARS telecommunications company by clicking here http://www.lars.co.uk/case-studies-jobs/bt-windy-hill/

Preston

Looking at the original Backbone hand drawn map, we can see that another of our important Cold War sites in Lancashire is featured on it. This is the one at Preston and the accompanying backbone document describes it as RAF Sector Operations Centre, Regional Commissioner’s HQ and Admiralty Radio Transmitting Station . To read a history of this site and it’s role in the Cold War see our web page here (Our Cold War Preston page). The site was connected to Hunter Stones at Skipton by ‘standby radio link’ and not microwaves. How this link would cope in the event of a nuclear attack is not clear.

Manchester

Again referring to the original map, we can see three unique sites that are marked as Baseband Connection Points at Manchester, Birmingham and Highgate in London. These all feed into the Backbone network, but not using microwaves. It’s not clear to us what these sites are, but we do know the following: In the 1950s secret telephone exchanges were built in these cities that could withstand a nuclear bomb attack and ensure telephone links were not cut off. These were known as the following : Guardian Exchange Manchester, Anchor Exchange Birmingham and  Kingsway Exchange London.  For details on the Manchester Guardian see our page HERE. However, by the time they were completed, Soviet bomb building capability had reached new levels of devastation and all three exchanges were no longer protected by their depth and could have been damaged or destroyed by an attack.

Heaton Park, Prestwich, Manchester

In the early 1960s  new GPO towers were built at  Heaton Park in Preswich near Manchester, Birmingham and London. The London one is the famous Post Office tower and it is known that this was used to broadcast television and radio signals. The Post Office tower also was used to broadcast microwaves for military communication and presumably fed into the existing Backbone system. In the 1970s the journalist Duncan Campbell was put on  trial for revealing secret military locations. At the trial the Post Office tower was referred to not by name but as Location 23.The fact that it did not appear on any map was pointed out by Kate Hoey MP in the 1990s, implying that it did have secret military links. She made the statement in Parliament, so that she could not be prosecuted for revealing what could have still been a state secret.

All three of these towers are what are called Chiltern Towers. They are of the same design as the two original Backbone ones in Staffordshire, which are  Sutton Common see picture here https://en.wikipedia.org/wiki/Sutton_Common_BT_Tower

and Pye Green see picture here https://en.wikipedia.org/wiki/Pye_Green_BT_Tower

Were the Heaton Park, Birmingham and London towers built as a backup system to link into Backbone, should the secret  telephone exchanges in those cities be hit ?

The Heaton Park tower is made of cylindrical reinforced concrete and is just over 72 metres tall (half the height of its more famous London contemporary). The English Heritage Cold War book states that this design was favoured for the Chiltern style towers as it had low wind resistance and could probably survive a nuclear bomb blast. There would be telecommunications equipment on the floors of the  tower, and these rooms had no windows. Above  these floors are the array of  aerials. The original ones were horn shaped, the cylindrical drum shaped ones came a little later, but both types are for the transmission and receipt of microwave radio signals.

If you want to see the Heaton Park tower up close then follow these directions:

Park at the St Margaret’s Car park in Heaton Park , just off St Margarets Road. Follow the path by the side of the reservoir up towards the Dower House. You can clearly see the tower rising out of the trees, and a path will take you up to the fence for a really close look. Head around the side of the hill for some great views out towards the Pennines.

In the 1990s our defensive communications switched to satellite systems, so Backbone and its connected nodes became redundant for defense purposes. However, they received a new lease of life as commercial aerials for mobile phones.

Even today, there is very little information about the original network to be had, either in books or on the internet. The best source is the English Heritage Cold War book by Cocroft and Thomas (full details below) and the National Archive which stores the original GPO Backbone Top Secret paper.

To view the declassified Top Secret papers on the formation of Backbone in the National Archives click here. http://webarchive.nationalarchives.gov.uk/+/http://yourarchives.nationalarchives.gov.uk/index.php?title=Backbone_radio_link_and_radio_standby_to_line_links_for_safeguarding_vital_communications