Went to my grandma's neighbours house to do a bit of plastering yesterday and happened to check over her CU (can't help myself). Noticed a large customisable box between the meter and the CU. Label on box said 'Glover anti-arc device'. I thought to myself '?????'. So I opened it up and had a look inside. Turns out there is just a Henley block inside joining the tails. I asked the lady if she knows anything about it and she said after they had a near-miss electrical fire an 'electrician' advised her to have this 'state-of-the-art' device fitted at a cost of ÂŁ500. He told her they are big in America but aren't widely used over here yet, but they can detect arcing and will cut off the supply and NOTIFY THE ELECTRICITY COMPANY by satellite. I was gobsmacked. Henley blocks have come a long way lately!