Mentioned with question marks in the reference books of Don Willis and Walt Lee (who credited Willis for the information) it was listed as a mysterious 1942 production, Willis seeming to think it was an alternate title for another Tod Slaughter movie. But there is no character by the name of Magnus Vann in any of Tod's films, to our knowledge.
The year 1942 is also a mystery, because it's also the year (almost) of the featurette "Soldiers Without Uniforms", a movie presented to the BBFC for a certificate on Dec. 16, 1941... and never released anywhere, under any title. In the cast were Tod, Ian Fleming, Ellen Pollock and Margaret Yarde. It was a Widgey R. Newman production.
In the British Film Yearbook of 1946 edited by Peter Noble, you'll find nothing about "The Vengeance of Magnus Vann".
But in the 1947/48 edition the title appears suddenly as an Ambassador production - or release - in the Tod Slaughter filmography.
Then the title disappears in the 1949/50 edition...
There are three possibilities:
a ) Ambassadors announced this title (between "The Curse of the Wraydons" and "The Greed of William Hart") but never made the movie. A real pity, with such a great title !
b ) They acquired the Widgey R. Newman featurette after Newman's death and (maybe) released it sporadically as a programme complement and under the "Magnus Vann" title.
c ) They wanted to release the Widgey Newman featurette but encountered a problem - maybe legal, or defective materials, etc. Who knows ? this "explaining" the disappearance of the title the following years...
Of course the only way to solve the problem would be to know the character's names in "Soldiers Without Uniforms" - if one of them is named Magnus Vann, this theory is good. If not, it would be interesting to know if a synopsis was made for "The Vengeance of Magnus Vann". It was probably not inspired by a play or a novel, as I consulted the Web zillions of times and never found this name anywhere.
Some ideas ?
Open, general discussion of classic sound-era films, personalities and history.