Hmm - think I saw the same setup over St. Albans/Watford area at the backend of last week, about 18:00 on Friday 15th IIRC.
As well as the airspace & conflict issues I was really intrigued by the structure - I couldn't work out how a single aircraft was supporting what appearerd to be a rectangular banner (rather than the more usual streamer-type arrangement)
Rgds
IHF