I collected a sample of the different types of feathers and the photo below show a selection of wing feathers, the bottom one being the outermost leading edge primary from the left wing and, for scale, about 145-150 mm long.
Having pored over Tracks and Signs of Birds of Britain and Europe by Brown, Ferguson etc, I am reasonably confident that this is a woodcock.
The next question is what predator was at work here? Well, given that this was in a north of England coniferous plantation, I reckon that the options are fox, stoat/weasel, sparrowhawk, goshawk or buzzard. If I'm right and its a woodcock then this could either have been caught in flight and brought into the woodland for plucking, or nabbed while on the ground.
First of all I've ruled out fox, weasel and stoat as none of the feathers had been bitten through - they were all plucked clean. So I'm inclined to a bird of prey kill. If its a woodcock then the size would probably rule out male sparrowhawk.
So is it female sparrowhawk, goshawk or buzzard? I'm not entirley sure but in amongst the feathers were these:-
In a fanciful moment I could put these down as ripped out from the chest of a goshawk as the doomed woodcock kicked and screamed then gasped its last....and, the oracle on such matters (aka John Steele) confirms that they are indeed breast feathers from.....a woodcock. Ah well, dream on.