The photo seems to have also ( or first?) appeared here:
http://www.vord.net/609/aircraft.htm
where it is described as appearing "in my grandfather's archive".
The grandfather was Jack Lister AE (1913 to 2003). He was a photographer in 609 (West Riding) Squadron between 1937 and 1943.
The "blotches" that appear on the version of the photo on the vord.net site are missing, so is this another copy of the photo or has it been "cleaned up"?
The 609 squadron, from November 1941-March 1942 was based at Digby. (The Stirling has the letter "Y" on the nose.)