Yes, one of these bad boys (link below). Installed late 80's when the house was renovated and extended, I was just crawling...30mA?
No, just dangerous and illegal.
Photos show it still in place, and the seals look intact.
http://srselectrical.co.uk/image/cache/data/SRS Electrical/DSC00632-500x500.jpg
Didnt say it was sensable. And as I did say, done by the vendor prior to the sale. Proberbly by his mate, who by appearances did it in the dark, one handed, using his teeth to strip back the wires.
How they did it in the guide shown in your link (that I linked to a photo of) I dont know, but thats not my house. I will have a look at my cut out for interest however. I dont recall seeing the seal but equally I have not looked for it. That said, if you did call out the DNO, would then not remove the fuse, wait for you to move the tails, and then put it back in and reseal it for you?
Daniel