In For The Kill

Apologies to those of you of a squeamish disposition....
Returned to the fields today to try and get a few more landscapes and was greeted by the sound of high pitched squealing. On further invesigation, this image of an adder(?) with a field vole(?) clamped firmly between its jaws was revealed.....
I trod very carefully for the rest of the photography session!
A look on large may help with species identification?