Hi Martin,
Unfortunately, I do not have this information. But your assumption sounds logical.
I need to check out the book from which this photo is, but i think it's from "Kraljevsko Vazduhoplovstvo 1918 - 1944" - ("Royal Air Force 1918 - 1944"), group of authors Dimitrijevic, Micevski, Miladinovic).
Two of them are members of the forum, maybe they know