Perhaps instead of cannon he meant machine guns?

The Universal wing on the Hurricane had one machine gun installed (on each side) and was capable of also carrying either:
– Rockets.
– 40 mm cannon.
– bomb.
Now the rockets and bomb could be carried asymetrically (rockets on one wing, bombs on the other).

Can’t recall if the 40mm Cannon could be carried asymetrically, seems unlikely though.

I would love to see a photo of a Hurricane with rockets and one 20mm cannon.

See also the following post:
http://forum.keypublishing.co.uk/showthread.php?t=88279