Pub owner wanted people to, you know, actually talk to other people in the bar. He had some copper mesh. He thought, hmmmm.
It isn't a perfect cage (one customer complained that she actually got a signal, and she was moved to another table). But I have no objection whatsoever to the bar owner who did this or anyone who finds it an enjoyable place to go (Sussex seems like a long way to go for a pint, but that's cause I live in _New_ England). Unlike active jamming devices, which endanger other people and equipment in a variety of ways, a faraday cage that that stops people in the building from getting a signal has only one apparent problem: what if you need to call for emergency services? The owner supplied a land line, so no worries there.
(Don't read the International Business Times coverage; their site did something to Firefox and I had to force quit to get out of it.)