My memory is failing.
 

OK my job for today is to install an external socket.

So IP55 rated socket purchased and I know I have at least two spare breakers left on my consumer unit, so it makes sense to connect this external socket directly instead of splicing it into the existing ground floor ring.

I rewired the house about 8 years ago so I know the routing of every cable in the house. or so I thought. One of my spare MCBs is in use. A 16A off the RCD side of my consumer unit. Now connected to it is a single 2.5mm twin&earth. So I have obviously run a spur to somewhere, but I can't remember where.

Circuits in use are 3 ring mains for ground, first and attic. Garage is off ground floor ring until I dig up the drive and lay a new cable at which point it will be connected directly to the consumer unit, 2 lighting for ground and upper, shower is off the RCD side and the last is the cooker. WTF is this spur for.

Well turned it off and it should eventually out itself. Meantime I need to book in with the quak for a dementia test quick before I forget to.

House alarm or outside light???

Finally found it, fan heater in the bathroom. Makes sense to be on its own circuit and RCD protected.

Oh no! It was your next door neighbour's dialysis machine!