Directed by Richard Eyre, starring Judi Dench, Jim Broadbent, Kate Winslet and Hugh Bonneville.

Novelist and philosopher Iris Murdoch was frequently described as the "most brilliant woman in England", a tag which made her mental deterioration from Alzheimer's disease all the harder to bear, both for her – while she was conscious of it – and for her adoring husband, the critic John Bayley. 'Iris' is a dramatisation of Bayley's memoirs of his wife and poignantly documents the painful loss of words from one who lived by them.

The film flickers between the tentative beginnings of Murdoch and Bayley's love affair in picturesque 1950s Cambridge to its twilight years in the 1990s. The young shy stammering Bayley (Bonneville) is entranced by Murdoch (Winslet at her intense and energetic best), a confident free spirited academic who admits to having had a string of lovers, both male and female. In an overtly self-conscious prefiguring of what is to come, Bayley likens her to "a beautiful maiden who disappears into an unknown and mysterious world every now and again – but who always comes back."

The story of young love unfolding is cut with the discovery by the ageing couple (outstandingly portrayed by Dench and Broadbent) that Murdoch is suffering from Alzheimer's and her rapid deterioration. Before the onset of the disease, director Richard Eyre skilfully depicts the couple's delight in each other's company. A shopping expedition is an opportunity for philosophical debate on mustard ("Wholegrain mustard? But surely any entity is whole?"), customer service ("Do you want premium points?" "Do we deserve them?" says an intrigued Bayley) and simple companionship. As the Alzheimer's progresses, Murdoch feels as if she is "journeying into darkness" – but she is not alone. Bayley is her devoted first mate, caring for her by himself for as long as possible in their increasingly chaotic house.

The film suffers from Eyre's assumption that people already know about Iris Murdoch, the exemplary mind and writer of 26 acclaimed novels. His decision to focus on the 50s and the 90s means that the middle period of her life is discarded and we never see her in her true prime. We are told of, rather than shown, her acute intelligence, making it difficult to fully empathise with its loss. He is also frustratingly enigmatic about her propensity to bed others – and of how Bayley lived with this.

A short running time of just 90 minutes pushes the film into focusing more on the illness than the person but 'Iris' is more than just another film about affliction – the fine quality of the acting by all four leads ensures that. Not the feel-good film of the week but undoubtedly a warm and loving portrayal of a true and enduring marriage of two minds.

Caroline Hennessy