The Capenhurst Tower

I published my original exposé of the now famous Capenhurst tower here on 15th April 1999. If you haven't already done so, I suggest you read that first and then come back here.

After I published it, several things happened within hours. First, a friend with a `sensitive' job had kittens. He thought that if his employer found out that he knew the author of such a page, it could ruin his career. Second, another friend warned me that if the press found the article, I would have no control over what they did with it: I could even find myself at the centre of a lot of hostile media attention. Third, Duncan Campbell phoned me up and said, ``Frankly, I'm not convinced''. This was all quite enough to give me cold feet, and on April 16th I deleted the article from the server. (I reinstated it on July 16th.)

In the intervening three months Duncan Campbell and I did a lot more research. Working with arguably the world's leading independent authority on SIGINT (signals intelligence) was in itself fascinating. The result was a rigour and depth of research which gives the story `legs' which my original article lacked.

I continued with my analysis of the tower itself: finding out more about the telecomms routes between BT and Telecom Eireann, and doing more detailed assessments of the microwave paths. This involved a lot of work. (One day I might write a detailed account of it, but that would be a big task. If you are into Fresnel zones, earth radii, link budgets, digital modulation schemes and height diversity it might interest you . . . otherwise probably not.)

Duncan started by playing devil's advocate. As he explained to me at the time, he wasn't prepared to give the story credence until all other plausible possibilities had been sought out, tested, and - if arguments were available - discarded. Part of him wanted to believe it, another part thought the project so vulnerable to exposure and so audacious (and so illegal) as to argue that GCHQ could not have mounted this venture. Between us we came up with about half a dozen alternative uses for the tower, and one by one we realised that each of them was incompatible with what we knew about it.

At Duncan's suggestion, I looked at the planning consultation file held by the local authority. I also followed his advice to photocopy the whole file. ``Copy first, ask questions later.'' Titbits may be more relevant than one first realises. We particularly enjoyed one bit of disinformation in the MoD's cover story. With a bogus hint toward the forest of National Grid pylons around the BNFL site, it said the tower needed to be located near ``a concentration of overhead electrical lines''!

We visited the tower on May 20th. One of our team brought a `camcorder' (3-chip DVC Pro) with him. This was Steve Holloway, a professional cameraman, who later shot and edited the Channel 4 News story. Unfortunately we had a rather safety-obsessed minder from BNFL, as well as the MoD Estates Disposal guy, and it took a long time to shake them off and explore the aerial galleries without them watching what we were up to.

Before we went up the tower, we only had a hypothesis about the tower's purpose. Trying to be scientific in our method, we planned to treat the visit as an experiment. The experiment was to see if there was evidence that aerials had been mounted facing the two BT sites and in no other direction.

Imagine our excitement when we found exactly that! Two neat little rows of bolt holes in the floor, parallel to the east and west windows only. Nothing had been mounted in the south window, confirming our suspicion that it and the north windows were decoys. (It would have been impracticable to mount aerials behind the north windows because the trap doors and hoists were in the way. The trap doors were bigger than shown on the architect's drawing: big enough to lift a drum antenna almost as wide as the windows.)

At this stage, we were both convinced that the hypothesis was correct.

Unfortunately Channel 4 News were not ready to run the story as their funds were short because of the Kosovo war. And at the time we had no independent corroboration of the story. Eventually Duncan got this from ``senior intelligence sources''. I don't know who or what these sources are, and I imagine he would not tell me if I asked.

Judy Aslett of Feature Story Productions was also in on this from an early stage. She and Duncan recorded interviews with various people in London: Madeleine Colvin (Justice), Nicholas Bohm (Cyber Rights UK) and Dr. Whitfield Diffie (co-inventor of the Diffie-Hellman algorithm used in public-key cryptography).

The following week, on Monday 12th July, I joined Judy and Steve for the shoot at Pale Heights and in and around Capenhurst itself. There was one Kodak Moment, while we were standing on top of the reservoir at Pale Heights. Two RAF jets flew past, very low . . . cue X-Files theme.

The story broke on Channel 4 News on 15th July. I thought Judy and Steve made a superb job of it. Judy is no techie, but her report was spot on. Normally, when telly people report on something I know about the result has invariably made me wince at the corniness, inaccuracy or whatever. This five-minute piece really cut through to the essential story and told it with pictures. Good pictures too.

Duncan wrote a front-page news story and a detailed feature article for the following day's edition of The Independent.

I was slightly surprised at the `GCHQ bugged Dublin' angle in these reports. For me the issue has always been `Did GCHQ bug Dublin illegally?'. To be legal, there would have to have been a warrant. If there was a warrant, GCHQ could have presented the warrant to BT, which would then have been obliged under the terms of its Oftel licence to provide the tap. Much cheaper, and much more discreet.

If it was legal, why did GCHQ do it the hard way?

Another weird aspect of this story is that it was so easy to rumble the tower's purpose. Here we had an odd-looking 158ft high structure, visible for miles around for a decade, built for a single purpose that was classified `Top Secret Umbra'. Anyone with a basic knowledge of microwave communications and a bit of initiative could have worked it out. Yet none of them did. Extraordinary.

Events after the C4 News broadcast have followed a predictable pattern. In Ireland there is shock and offence at HMG's dirty little conspiracy. The Irish government has instructed its ambassador in London to demand an explanation. HMG itself trotted out almost word-for-word the standard, irrelevant quasi-statement. Some of the other media tried to run the story, but they had been well and truly scooped and had no information of their own. Apart from a brief effort by the BBC, as far as I know no other UK media have touched the story.

At least it made Slashdot.

I write this just ten days after the story broke on C4. For SIGINT anoraks and anybody who is worried about governmental nosey-parkering, the Capenhurst tower has become part of the Echelon furniture. The story has disappeared from the public gaze as suddenly as it arrived. It seems that few people give a damn.

Last updated 25th July 1999

© 1999 Richard Lamont