Six Minutes to Midnight: Who do you think you are kidding, Eddie Izzard?

Approach this harmlessly silly prewar romp – arriving on Sky after a deferred theatrical release – with no prior knowledge and, within half an hour or so, you will almost certainly find yourself hoping it is based on some sliver of historical truth. Why else would Eddie Izzard conceive such a thing? Heaven forbid such an admirable figure had bothered to make all this rubbish up.

Sure enough, there really was, until shortly before hostilities commenced, a finishing school for the “daughters and goddaughters of the [Nazi] high command” on the English south coast. There is potential here for a camp entertainment of the silliest order: Invasion of the SS Schoolgirls; Netball, Nocturnes and Nazis; The Belles of Saint Swastikas. The possibilities are endless.

Izzard has instead written herself into a variation on Hitchcock's The 39 Steps. Strong in the right sort of role, the indomitable comic, who has completed more marathons than you have worn underpants, does get the chance to run across numerous grassy plains, but she otherwise struggles with her own – cowriters include Celyn Jones and director Andy Goddard – drab variation on an overworked English cliche. Every now and then, the tiniest hint of parody sneaks out and we get a sense we're watching a pseudo-Richard Hannay or a proto-Bulldog Drummond. But the film quickly slips back into pale retread rather than promising lampoon.

Thomas Miller (Izzard) arrives at the school shortly after another teacher has disappeared. We soon learn he is investigating the mystery for some corner of the British secret service. The deeper Miller probes, the more he encounters hook-nosed men who first offer sanctuary before pulling out Lugers and banishing verbs to the end of sentences. You've all seen Where Eagles Dare. You know the sort.

So broad are the cultural references that the setting could be taken for a recreation of interwar English life on Westworld. You just know the protagonist and his contact are going to meet at a performance by a Max Miller type. Goddard, a Downton Abbey alumnus, directs with the flatness you expect from a YouTube video explaining the correct way to hang a painting.

It would be nice to say that Judi Dench, inevitably the headmistress, elevates the project, but even she can't get gas back into the plummeting Zeppelin (wrong war, I know). Still it's not every film that has a shot of the great Dame straightening her arm and yelling "Sieg Heil!" at the wireless. We'll give it that.

On Sky Cinema from March 26th