Your engine and frame numbers match, the bike leaving the factory on 27th Oct 1942. As the Allied invasion of Italy began on 3rd Sept 1943 I think we can reasonably guess that your bike took part in the Italian campaign but was left in Italy afterwards, as quite a number of W/NGs were. Given the lack of an engine change, it may be that the bike was captured, or that it saw little use, perhaps being left in a stores dump until the war ended. You might infer more from the general level of wear and tear, notably the bore size.
36 4G, 37 VH, 54 KH(A), 75 Healey 1000/4, 52/53 ex ISDT KHA (project).
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.