You have captured the rat very well, I don't remember ever having seen that before. I would have thought the stoat would see off a rat, they are the same family as the Honey Badger and share their ferocity if not their size.
It reminds me, I looked out of my window the other morning and saw a hedgehog fighting with a squirrel. After a while it looked like it might have been a draw but the hedgehog went on to win on points!
Remarkable shots! I'd back the stoat too, but a rat - particularly a buck - can be a formidable animal and a lot of predators instinctively try to avoid a major battle because they can get badly injured, even if they win, which can impair their hunting ability.
The Honey Badger (Ratel) seems to be a law unto itself. They're fearless, incredibly tough and tenacious, and I've seen film of one pushing lion off a carcass.
We often use the car as a hide, so with the camera on the wife's lap and eye's peeled
we spotted the stoat up the road and drove slowly towards it, but it still dived into the
hedgerow. So I jumped out the car stood at the rear with camera on my monopod and
waited. Sure enough it came back out, got some shot's then disappeared.
I think it must of gone down a rat's nest because out it came being chased by the rat,
it all happened in a flash so just shows it pays to be ready.