TV Detector Vans
In the UK, you need a license to watch TV. The proceeds from the license fee fund the state broadcasting company, the BBC. In order to enforce this, the government sends out TV license inspectors, who go into unlicensed properties to check whether there’s a TV present. Of course you don’t actually have to let them in; they have no legal power! They are real. I had one visit once. He came in and asked what my TV was. I (truthfully) told him we watched Netflix and Youtube on it, and didn’t own a TV box. He left.
They also have TV detector vans, which drive around and detect which houses have television sets.
On The Existence—or Non-Existence—of TV Detector Vans
On the one hand TV detector vans don’t exist. Wikipedia calls them an “urban legend”. It goes on to say that no detector van has ever enforced a TV license fee. This appears to be true. The BBC has never registered a patent on the operating principles of a TV detector van. The principle of detecting a broadcast receiver is itself pretty fraught. How do you detect whether something is absorbing a signal?
On the other hand, they do exist. There are pictures of them and eye-witness accounts. The Post Office Electrical Engineer’s journal details the successive development of multiple types of detector: initially, old-timey cathode ray TVs could be detected by their magnetic field (which deflects the electrons to a specific point on the screen, producing the image). Then later on, receivers could be detected by the signals produced by their local oscillators (sometimes, the easiest way to detect a 50 MHz signal is to produce your own 50.01 MHz signal and detect the 10 kHz interference waves).
To make it a slam dunk, in 2013, the TV license inspectors applied for a warrant (to actually legally enter a property) based on some evidence from their detector vans. Several Freedom of Information requests have reproduced the exact text of the warrant, and it’s this:
5. A television display generates light at specific frequencies. Some of that light escapes through windows usually after being reflected from one or more walls in the room in which the television is situated. The optical detector in the detector van uses a large lens to collect that light and focus it on to an especially sensitive device, which converts fluctuating light signals into electrical signals, which can be electronically analysed. If a receiver is being used to watch broadcast programmes then a positive reading is returned. The device gives a confidence factor in percentage terms, which is determined by the strength of the signal received by the detection equipment and confirms whether or not the source of the signal is a “possible broadcast”
Pretty cut-and-dry here. The warrant was granted, and the TV was found.
I’m sure some of you can already guess the punchline. That long string of technobabble is just describing a camera. They even call it a “camera” later in the warrant application. Whoops. Maybe they don’t exist.
So what’s the answer here? Either way it’s kinda nuts. Maybe the BBC actually did develop and build TV-detecting technology just to build detector vans and drive them around detecting TVs. Maybe they published multiple articles explaining how one might work, built several distinct generations of detector vans which looked sci-fi but also different, and then put their regular TV license enforcers in them, and then lied about it for years up to this day.
I think I lean towards the original generations being real. I think the British Government of the 1950s had the chutzpah to actually build a few of these things. At some point, the technology ceased to be viable (and indeed very few people claim to have seen a TV detector van today) and were quietly wound down. They probably kept up the hoax for the purpose of deterrence. If this is true, I think it’s unlikely but not impossible that they ever labelled non-functional vans with “TV Detector” and drove them around. I think we can explain the lack of direct convictions with the fact that a TV inspector van would only ever have been sufficient evidence to get a warrant, not an actual conviction (in the 2013 case they had pictures of the guy and still had to get a warrant).
The idea of “TV detector vans” seems like a passable cover for other sorts of surveillance.
This makes some sense, on the other hand, what kinds of covert surveillance could be done in the 1950s/60s and would be most effective when done by neither a van labelled “Police” nor a van labelled “Robinson’s Garden Equipment”? I’m struggling to find the specific use case for a van which is clearly a state surveillance van, but slightly more obtuse.
If it looks like the van in the picture, the antennas might be needed for surveillance functions. If you have visible antennas claiming it to be a normal police van or “Robinson’s Garden Equipment” would not do the job.
This person has been keeping track of their dealing with the BBC wrt to their choice not to get a TV license since 2006 (I believe at some point their SEO was so good that searches for ‘bbc TV license’ brought up this person’s website, rather than any official source)
They document things like the technology claimed to be used, and the results of Freedom of Information requests
Other fun pages include bogus/contradictory numbers supplied by the BBC, people spotting vans in the wild, and why the BBC’s threatening letters request people to not ‘write below this line’
Interesting. I note that the vans in the (recent) pictures just state “TV License Enforcement Van” and don’t claim to be able to detect TV sets.
Some of my colleagues (including Markus Kuhn) do research into “Tempest” where you eavesdrop on the RF emissions of electronic equipment.
So, it is certainly possible to do this.
It is also, probably, not a cost effective means of making sure people pay their TV license fees. It seems that what TV licensing actually does is assume nearly everyone watches TV, and send a threatening letter to everyone who doesn’t have a TV license.
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Conspiracy theory version: if the government is doing Tempest attacks on a small number of high value intelligence targets, checking that people have paid for their TV license is a great cover story for why you have a van full of RF monitoring equipment parked in the street.
Compare the Simpson episode with the “Two guys from Quantico” pizza van.
Also, at some DARPA event (unclassified, and in front of journalists, so this story is ok to repeat here) some three star general, talking about infosec, makes analogy to “strategic deployment of stay dogs”:
Suppose:
you do not have enough explosives-detecting sniffer dogs
You do, however, have as many untrained stray dogs as you want
The enemy does not know which kind of dog is which
The principle applies to more than just sniffer dogs at check points.