This caught my eye:
A grey-phase Gyr the other day in Highland region.
I can't remember any other grey-phase mainland Gyrs other than a couple of one day birds in the early 90s. White-phase birds are much more usual and as a grey bird is unusual bird for us here, I thought I'd post a link to the pics.
Photos here but large falcons are not my strong point. The description was of a long-winged and long-tailed huge falcon.