That looks an awful lot like an even more worn Tort I caught at Dingestow a few days ago (http://gwentmothing.blogspot.co.uk/2016/06/a-few-more-dingestow-moths.html). I still can't work out what mine is, so I'm afraid it's going to need to be gen det. Yours has similar mid-wing markings to mine (though your photo makes them much clearer), same pale palps and same dots along the termen.
Thanks Sam. I have kept it for future reference but it would be very interesting to hear what yours is.