The last film playwright-screenwriter William Nicholson wrote was Breathe, a based-on-a-true-story drama about a deeply happy marriage challenged by the inability of the husband – a polio survivor – to breathe without a respirator. With Hope Gap, Nicholson’s adaptation of his own late-80s stage play The Retreat from Moscow, the dynamics are flipped, presenting the story of a couple who have just about everything a middle-class retired couple could want – security, a lovely house on the English south coast, their health – apart from a happy marriage.

Light-stepping, terminally recessive schoolteacher Edward (Bill Nighy, dialling it down to give one of best performances in years) has fallen out of love with his perpetually critical, intellectually rigorous wife Grace (Annette Bening), who has been compiling an anthology of poetry for years. When their adult son Jamie (Josh O’Connor, exceedingly good at projecting shy vulnerability beneath a superficial cheeriness) comes for a visit, Edward reveals his plans to end the marriage and move out, forcing Jamie to act as a mediator between his muddled father and raging, wounded mother.

At one point, Jamie talks about how happy he had been years ago, walking to Hope Gap on the coast as he swung between each parent. That symbolism, echoing how he’s trying to manage his parents now, is painfully on the nose. In fact, there are a few too many whopping bits of literary clever-clogging in the dialogue, such as a reference to how the revert function on Wikipedia entries operates as a metaphor for soured relationships.

Nevertheless, the performances are terrific, especially from Bening who adds yet another deeply nuanced study to her gallery of complicated, smart women of a certain age. It’s up there with her turns in The Kids Are All Right and 20th Century Women. Anna Valdez-Hanks’ limpid cinematography, capturing the cool, flat light of the British seaside, is also a plus.

Hope Gap is in cinemas and on Curzon Home Cinema from 28 August