Why is taking photographs not allowed in Spitalfields Market?

The IPKat noticed this thought-provoking and slightly worrying post on the popular and prolific blog BoingBoing. A friend of the blogmeister Cory Doctorow went yesterday to the (publicly open) Spitalfields Market, and took an unremarkable photograph (right). He then says:

Right after I took the shot, though, a large security guard walked directly up to me. “We don’t take pictures in here.” “Oh?” I said. “Yes,” he replied, reaching for my camera. “We’ll have to delete that.”

The photographer managed, however, to escape with life, liberty and photograph intact.

The IPKat wonders why Spitalfields Market is taking against having photographs taken, particularly given there is a specific exclusion under UK Copyright law to allow this kind of thing. Since the many commenter on BoingBoing don't seem to have any idea, could any of the IPKat's knowledgeable readers cite any law that would either support or further discredit this view?

Given some of the comments below, the IPKat further wonders whether the recent Met campaign, evidenced by the (completely genuine) poster below, has anything to do with it...