Richard Attenborough, David Hemmings and Alexandra Stewart play three con artists planning a big-time scam. The object is to sell ammunition to a group of African militants -- or at least to pretend to. The trick is to keep at least one step ahead of the militants, lest the tricksters end up full of holes. A serviceable Len Deighton espionage novel was the source for Only When I Larf, which hooked up the material with "mod" gags about '60s fads and foibles. In the same spirit, the usually straightforward director Basil Dearden makes like Richard Lester, with a multitude of jump cuts, zoom-ins and hand-held shots.
~ Hal Erickson, All Movie Guide