Sir Victor Goddard, retired RAF officer, revealed this (now famous) photographic anomaly -

The snap was taken at the Royal Navy airbase HMS Daedalus in 1919 on the day of the funeral of the squadren mechanic, Freddie Jackson – who had been killed two days earlier in the propellor of an aeroplane.

It is said that it is undeniably Freddie’s features which mysteriously appear in the photograph (image enlarged on the left for clarity).