Pure guesswork on my part but could the fact that these are RAF photos of the late 40s be at the root of this mystery? At that time(before satellite photography)aerial photos taken from planes would be examined by eye for hostile military installations, troop movements, airfields etc. Those examining these photos would need to be trained. Could it be that there was no plane but that it is a plant to be found (or missed) by the trainee spotters? As such, it was perhaps superimposed on the photo, painted onto the negative or however such things were then achieved, for training purposes; the enemy plane hiding in plain sight. It would need to be placed on a big enough piece of land but not where it would easily stand out, like the middle of Kennington Oval or the boating lake in the park, a villa's carriage drive being ideal. Just a thought. Another possibility occurring to me was that it might a dummy (inflatable? or partly so?). A lot of dummy aircraft were positioned around England during WW2 to confuse German spotter planes as to the disposition of Allied airbases and reserve fleets. Columns of inflatable and mock up tanks were also common, particularly in north Africa. There must have been many surplus dummies knocking about in 1946. Quite why one might end up in this garden is another thing.