Originally Posted by sycamore
I think the wings are on upside down;serials underneath,unless it flew inverted....
Serial placement noted here too, and no serials shown on the box artwork. Installing the wings upside down might have affected its flying characteristics, though - perhaps that explains the damage to the tip if the fin?
Union Jack ... my Reference Book [Bruce Robertson's 'British Military Aircraft Serials'] agrees with your perspective - J9842 was one of a batch of 37 x Westland Wapiti IIA.
[MPN11 removes anorak]