It's a pine marten, a protected species (though not by farmers if rumour is to be believed). They can be vicious creatures (who can blame them in a difficult world) but are very beautiful. This one took itself off to the back door next.
I was poised with the camera on the inside of the door, waiting for its nose to poke through the dog flap. If it had scratched that door, I'd say it would have been through in a trice. I put the lock on the flap. Didn't fancy a confrontation between pine marten and elderly dog.
A while later it was back at the bird table. I opened the half door and it came towards me, pointy little nose pointing. We had a chat before it lolloped off. So much for the shy retiring pine marten nature. Not a bother on it.
Post Script. We found s/he curled up in the greenhouse. When I came back with the camera the fluffy tail was all we could see: