MT 121/2

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London - South Wales motorway: proposed monorail and hovercraft service to London Airport

Date range1958-1964
LocationNational Archives (see all files stored here)
CatalogueSee entry
File baseSeries MT, subseries MT 121


This file seems quite ill-at-ease in a series reserved for discussion of special road projects, but the documents that reside here seem to have been retained by the division of the Ministry of Transport concerned with the London end of the M4, at a time when they were being consulted on the impact these lunatic proposals would have on their motorway. For the most part this file is a flight of fancy into experimental modes of transport that wouldn't have looked out of place in an episode of Captain Scarlet.

Ernest Marples, as Minister of Transport at this time, seemed to have started open season on crackpot ideas for a high-speed link from Central London to the then-new Heathrow. The proposals shoved through the Ministerial letterbox were:

  • a British Rail plan for a rail link, with services from Victoria using existing lines to reach Twickenham, then branching off to the north on a new line that would follow the south and west boundaries of the airport before finally arriving in its centre.
  • a monorail running above the A4, which was stamped flat by the Ministry when they demanded that passengers be able to de-train at any point on the route. An isolated rail running on pillars above a motorway made that impossible and the idea was dropped.
  • a hovercraft service, outlined below.
  • a completely new idea called a Geotube, outlined below.

The hovercraft

The hovercraft proposal was to fill in the Grand Union Canal, put the water into a pipeline, and pave over the top with a pre-fabricated track on which hovercrafts could run at high speed. A bridge would then carry the hovercrafts over the M4 and into the airport somehow. The Ministry noted that while it might be nice and quiet inside the hovercrafts, it would be hellishly noisy outside them, and most unpleasant for houses backing on to the canal; that the volume of water travelling down the canal was enormous and not easily piped, and in any case there would need to be easy maintenance access to the pipe underneath the track which would add considerably to the cost of construction; and that the idea was more to do with an excitement about the technology of hovercraft in general than it was to do with practicality.


The Geotube was a very serious proposal for a lightweight way to add new rail capacity by suspending tracks above existing railways or roads and running small tube-style trains through them. The name came from the construction of the suspended railway: trains would run in tubes, made of very lightweight aluminium mesh in a criss-cross pattern that made it very light and very strong, so supports could be slender and widely spaced. Two tubes would run alongside each other at all times, with accesses to a walkway between them, allowing for detraining and maintenance access. The trains themselves almost filled the tubes, with a pickup rail at the very bottom and rubber wheels almost halfway up the sides to save space. There is a full report here on how the system could be feasibly and realistically constructed, and how terminal facilities in Earl's Court and Heathrow might operate, along with a theoretical extension to Gatwick.


All of these plans were halted by Marples' insistence that he had just built a motorway to Heathrow and he wasn't going to spend money on a second high speed way to get there just yet.

People with camera copies

Chris Marshall has a partial copy, including the Geotube report.