To reply to Dunhovrin, a couple of the chaps (I think SPIN was there) had a cannon made from nothing more than an old map tube which puffed away quite nicely on top of the Hazbar until someone squirted some 'borrowed' medical oxygen into the thing.
Resulting explosion got the French and the Italians (who were on the other side of Skopje airfield) to stand to, and Cdr JHF to stand to apologise a pair of rather irate Colonels.
Or something like that