The producers of this thriller use a foreword to tell us that the prison escape method shown in the film has actually been used.

At least that serves to scotch one of the many implausibilities in their story, which gets by on its exciting action sequences and a rich variety of supporting characters.

Hard to tell at times, in fact, whether director Tom Gries is playing it all in light-hearted vein, although the bloody events of the last few reels seem to contradict the theory, and the escape itself is full of tension.

But a key part of the action involves Randy Quaid convincing prison guards that he's a girl.

Now Mr Quaid is about six-feet-five and weighs 200 pounds...