Can;t be a tax van, as they are only pulling motorists PASSING them, so the cameras wouldn't be able to see the tax disc from BEHIND the passing cars would it?

It's the same van I see in stings all over North and East London. It's unmarked so as not to draw attention to it.

Aprrently it doesn't have to be marked cos it's not doing you for speeding or anything - it's observation, and it films the police further up the road "for protection" (evidence more like!)