The BBC's flagship sitcom Dad's Army about the pensioners who worked to guard the home front while the young men were away is a much-quoted British institution. Many were apprehensive at the news that Jimmy Perry and David Croft’s sitcom was to be adapted for the cinema, for what need was there to pay homage to a TV show that got it right the first time?

But while Oliver Parker’s new Dad's Army film does not reach the comedic heights of the original BBC series, it is as gently humorous as it is charming. Occasional outbursts of slapstick build to a fun, sweet-natured film that pays tribute to the original.

The feel-good comedy is greatly boosted by thespian royalty Bill Nighy, Tom Courtenay and Michael Gambon playing the aged platoon.

Set in Walmington-on-Sea in 1944, the film follows visiting journalist, Rose Winters – played with plenty of glamour by Catherine Zeta-Jones – whose interest in the village Home Guard platoon is somewhat suspicious. The drama cranks up when MI5 discovers that a German spy is lying concealed in the fictional British town sending messages to Berlin. The Home Guard's incompetent crew of pensioners must step up to the plate and defend their country for the first time.

Some of the film's attempts to replicate the humour of the television series feel feeble: while in the original, Captain Mainwaring’s mistaking the bull for the enemy (which then proceeds to chase the platoon around a field) would set the scene a broader joke, in the film this is the joke, and later almost exactly the same gag is repeated when Private Godfrey mistakes a rabbit for a German spy. Cheap double entendres, too, make Parker's film feel a little sloppy.

That said, Zeta-Jones exudes charm as visiting journalist Rose Winters, and Michael Gambon raises laughs as a blundering buffoon. Fans of the original, too, might enjoy the cameo entry of Ian Lavender as Brigadier Pritchard.

The humour is more silly than subtle, but the frothy fun of the sitcom shines through.

Dad's Army marches outdoors...

Dad's Army is being screened in London parks this summer as part of Luna Cinema's open-air film programme - book your tickets now!