I got a PM guess, the Vickers type 161, which meets all the clues so far but is not the plane your looking for. I think that means it's time for another clue or two....
I'm looking for a plane...
1. It could have been used as inspiration for some of Klunk's inventions in Dastardly and Muttley and was about as successful.
2. While ill conceived it did actually fly.
3. As implied above only one was ever built.
4. The design was developed to meet a specific threat.
5. It was equipped with a 1½-pounder cannon.
6. plus two machine guns
7. Twin engines.