We heard this raven before we saw it. It flew off just after I had taken the picture. We later saw it mobbing a common buzzard that was hunting over the fields
No interactions present.
You've clearly identified this as a Raven in the title and description but haven't entered anything in the identification section!
I agree with your ID though - the very heavy bill and wedge shaped tail can be seen in the photo (size and calls are not discernable, but would have been additional pointers at the time).
Can a single bird "mob" anything?
Pedantry apart - excellent photo of a very wary bird!
Is that a coloured ring I can see on its leg?
Yes, it is a yellow ring. Could not see any other rings or details, I'm afraid.
Lat/Lng: 54.1, -3.0
OS grid ref: SD3973