Take A pair of warring parents, a sickly grandad, three brilliant kids...and what have we got?

Answer: the most enjoyable British movie of the year!

One that will lift your spirits, tickle your ribs and tearfully remind you of elderly relatives past and present.

True, it begins with an acute sense of pain, but that’s where the children come in  – lightning conductors of the human kind.

Doug (David Tennant) and Abi (Rosamund Pike) are living a daggers-drawn life, but they must put aside their traumatic divorce for the sake of keeping up appearances.

A 75th birthday party for Doug’s father Gordy McLeod beckons by the Scottish coast – and nobody could miss that – not when Gordy is played on this kind of form by Billy Connolly.

Least of all the three grandchildren.

Four-year-old Jess loves a brick called Norman, while middle child Mickey’s obsession with Vikings will soon come in handy.

Eldest child Lottie, nine, must keep the divorce a secret, so she keeps track of the lies she’s expected to tell by making jottings in a notebook.

Some of the early scenes play out like a TV drama, whether it’s the parents bickering or the motorway sequences shot in low budget fashion.

But the characters grow on you in a seaside world of impossible beauty.

The mid-section, in which the children play with grandad is breathtakingly good, full of wisdom and fun, inquisitiveness and the kind of impulsive behaviour that only minors can have.

The youngsters’ performances here make this the best film of its kind since Little Miss Sunshine (2006) and a return to the kind of captivating British film industry family values associated with Whistle Down The Wind (1961), Kes (1969), The Railway Children (1970) and Millions (2005).

Meanwhile Connolly, 71, delivers an imperiously heartfelt performance while drawing on his own mixture of exuberance tempered with the sensitivity of what was then his own private cancer battle during filming.

Co-writers and directors Andy Hamilton and Guy Jenkin are still best known for their TV work on shows like Not The Nine O’Clock News, Drop The Dead Donkey and Outnumbered.

But their latest effort behind the camera confirms their potential to outperform Dick Clement and Ian La Frenais, the writers of hits like The Likely Lads, Auf Wiedersehen Pet and Still Crazy who never did get a joint directing career off the ground.