Bit of background. We moved house at the end of last year. For a while we had a few problems with the cat's piddling where they weren't meant to (under the tv for one) We put a litter tray in the kitchen and the bathroom upstairs and they have access outside all day. Problem solved.
Came back from a few days away and found out Brian had peed and pooped in the log basket 
This evening I was on the netty myself, big cat goes into the litter tray, Brian squats down and makes a lake. He ran away and is hiding from me so he knows he's done something wrong. Not really sure what the next step is with him. He's 3 and a half and we never had trouble with him before except when he had a urine infection as a kitten.
Any advice very welcome!