Accessibility of joints only entered the regs in 2012 though, so you could expect to find a lot of these around. At least it was mechanically protected by the tiles. There are a few methods for joining that in situ that meet the regs if you are going to tile over it again.
I want you to do any future work I need done on my flat, you strike me as very wise in these matters.
My electrics area bloody mess, opened up a couple of sockets to switch them out and it was a quick "nope" and reattach.
Accessibility of joints only entered the regs in 2012 though, so you could expect to find a lot of these around. At least it was mechanically protected by the tiles. There are a few methods for joining that in situ that meet the regs if you are going to tile over it again.