History

Information on this route has been compiled largely from planning applications and a map showing plans for the trunk network in 1988. There remain three significant "unknowns":

• What was the overall plan and purpose, particularly west of Salisbury?
• Did the two "completed" sites carry traffic?
• At what point was the plan abandoned?

The following is known information from public records:

Planning applications were submitted for four new sites: Tatsfield (approved December 1983), Truleigh Hill (approved), Goodwood (rejected 1984) and Dean Hill (rejected 1984). Approval was given on appeal for Dean Hill in June 1986 however the site was never developed. Goodwood was also allowed on appeal in 1986 but discussion continued until around 1990, again without any development. Further details of the planning applications are shown below, where available. All four sites are shown on a BT map of microwave stations issued in the 1980s - but it seems this reflected the plans rather than progress.

The application for Tatsfield included a map showing an overall route. This is unsuitable for inclusion (copyright and poor quality) but shows the route starting at "LTT" (London Telecom Tower), running south via Tatsfield to Truleigh Hill. The map shows two possible options to the west, either via a site in the Midhurst area or Goodwood, continuing via the existing sites at Butser Hill and Thornhill, then Dean Hill and ending at an unknown site near Upavon.

Less definitive information is found on a map of planned trunk routes. The System X "DMSU" (Digital Main Switching Unit) at Salisbury is shown with 11 GHz links apparently to London, Reading and Exeter. The planning appeal for Dean Hill notes that the site was required "...to relay signals from various sources to Salisbury where there is an important switching facility in the national trunk network...".

A 1984 summary of BT's grounds for appeal for the Goodwood site provides some confirmation of the "big picture": The proposed microwave radio station, comprising a building to accommodate the radio equipment, and an aerial tower 28.9 m high is required to carry every available radio band for national and international communication networks by way of the Goonhilly satellite earth station, a new earth station near Yeovil, and transatlantic submarine cable landings on Cornwall.

Despite this, the detail of sites beyond Dean Hill seemed sketchy and by late 1986 the decision had been taken to expand existing facilities rather than construct a new Earth Station.

The following is background commentary based on understanding of the "current" network in the early 1980s, the general plan at the time, and the impact of not buiding the sites at Goodwood and Dean Hill.

Traffic from Goonhilly (and some from the second Earth Station at Madley) was carried over the London - Bristol trunk route. This included some cable provision but also used microwave links. BBC and ITV "vision circuits" serving Wales and the South West were also carried over this route, together with inland trunk telphony. This meant the SHF bands were reaching full capacity between London and Bristol.

Plans for an all-digital trunk network would introduce new links at 11 GHz with longer-term plans to clear the existing bands for digital links. This would not initially create significant additional capacity and existing traffic had to be maintained. The only way to add capacity at SHF was to use a separate route: going south rather than west from London allowed this possibility.

Each System X Digital Main Switching Unit (DMSU) required a connection to every other DMSU and the use of 11 GHz links formed part of this network. There was a deliberate decision for the network to include a mixture of radio, fibre optic and conventional cable routes. DMSUs were planned for Bristol, Exeter and Plymouth, also Portsmouth and Salisbury. It may be the new SHF route was expected to distribute traffic between these locations and to/from London.

A 1988 map of the as-built trunk network shows a fibre route to Salisbury. The planning delays, cancellation of the Earth Station and the increased use of fibre may be the reason why BT did not proceed with their plans for Goodwood and Dean Hill. That leaves open the question of an interim link using the two completed sites together with those already available and some form of site sharing at Goodwood and Dean Hill.

In practice the existing structures at Goodwood - which would have been dismantled if the BT plan had gone ahead - were wooden towers from World War II. They would not have been able to support the large dishes used in the BT trunk network and no proposals to use these structures were put forward by BT. At Dean Hill the plan was to "take over" a site originally developed by Pye Telecommunications which consisted of a relatively short guyed pole - unsuitable for use by BT. The planning appeal process discussed the possibility of sharing a more substantial tower nearby, then operated by the Ministry of Defence, but it was argued that there were still issues with the capacity of the structure and with agreeing terms for BT to have access.

My conclusion, subject to correction if new information becomes available: neither Dean Hill nor Goodwood were used by BT. As a result, no traffic could have been carried west of Truleigh Hill and it seems unlikely the section from London would have been commissioned.

Planning Details