A few years ago I had to research the wearing of Army/RN/RAF wings on other Services' uniforms for a real issue for regulars (no more details - it might imperil my incognito!) . The rule then - this was 20 years ago - was that RAF Wings could be worn on army uniforms and vice versa.(So Wills and Harry are both right!). The RN - unsurprisingly? - said RN Wings could only be worn on RN uniforms, and no other wings could be worn on them. Not sure where that puts RM?? Suppose the RN counts them as Navy......