Although the overall shape corresponds, it can't be from a Mosquito, as, apart from appearing to be too small, even if a section of the part, the Mosqutio had fabric-covered elevators and rudder, although the ailerons were aluminium.
The remains of the vertical writing do throw things off a bit, and it could be that this part was used as a signpost at some time, as suggested. Dave, the control surfaces on the J5 in your pic are also fabric covered, so that one's out too.
Given the approximate dimensions provided, and with the possibility that there is a section missing, I think it is more likely to be an elevator, or, if a rudder, from a relatively small aircraft.
The overall shape is, I admit, very much similar to a De Havilland style, but the metal covering again (probably) discounts that stable. I had thought perhaps the outboard section of a P47 elevator, but the right angled balance horn area is incorrect.