History
The 1956 "Backbone Map" accopanies the paper "BACKBONE RADIO LINK AND RADIO STANDBY TO LINE LINKS FOR SAFEGUARDING VITAL COMMUNICATIONS" available at the National Archvives, reference CAB 134/1207. The full text has been transcribed
The scheme was not built as initially discussed. Significantly the "protected" buildings were not provided and a number of substitute sites were used. Even on the original map, however, there was an expectation that sites for "Backbone" would carry television links, for example at Charwelton. The principal north/south route was diverted to terminate at Craigowl (Dundee) with other changes north of Hunters Stones however the section south of Manchester was largely as envisaged.
The 1956 map shows three different categories of traffic ("Backbone", "Standby" and Television) and unfortunately the distinction between two types of dashed line is not clear. This feature will be expanded to detail the as-built network which became operational in the mid-1960s. In effect this was a combination of the re-routed "Backbone" with the addition of some of the "Standby" branches. Re-organisation of defence functions meant that some of the original destinations no longer needed to be served and with a few exceptions the sites eventually used were shared with television and general telephony links.
For many years "Backbone" remained a secret network within a network - indeed previous research had tended to indicate it was completely absorbed into the general network. Papers detailing responsibilites for emergency provision by British Telecom have revealed that a separate "Backbone" was retained until the mid-1980s but by that time it was becoming difficult to maintain and it was proposed to transfer the remaining circuits to the "commercial" links.
