Andy Serkis’s directorial debut charts a topic so worthy and decent that it’s a real pain in the nether regions to have to haul it over the coals. In fact, maybe the coals don’t quite need to be involved – nor too much hauling – but there are grounds here to not quite give this quite the hearty fist bump that it seeks.

A true story, audiences are steered into the world of moneyed British privilege in the 1950s. Andrew Garfield commands his best plum-filled accent as Robin Cavendish: an adventurous young aristocrat and his well-meaning wife Diana (Claire Foy). Reclining in the tropic climes of India and traipsing the African landscape, the couple bask benignly in the spoils of their accumulated wealth and the colonial subservience of the denizens around them. This postcard picture of happiness is only enhanced upon news that Diana is pregnant with Robin’s child.

Sadly, this is the point when the coils of marital utopia are bent out of shape, as Robin one day collapses in the midst of spinning a hula hoop around his waist after a long game of tennis. Initially dismissed as the result of overexertion, he wakes in the night to a state of increasing paralysis. Saved from slipping into a coma, he is told that he has succumbed to polio.

Britain in the 1950s was not a place that offered anything in the way of accommodation in wider society for the disabled. In fact, it was much to the contrary. Wheelchairs did not exist and polio victims were consigned to hospital wards, where they were laid out prostrate on beds with around-the-clock care and no real quality of life. The reason why this story needs to be told is because Diana’s unwavering loyalty brought about change. Whilst she accepted Robin’s diagnosis, she did not accept the de facto methods of maintenance. Why should there be immobility? Why should there be consignment, containment and relative isolation?

Through her network of family and friends, in the ensuing decade, she set about upending the way in which Robin would spend the remainder of his days. In the process, she set a benchmark for practices towards the disabled that are all around us today.

As you can see, this is all important stuff. It is a pity then that even with the sumptuous cinematography (courtesy of Robert Richardson) and assured hand of Serkis, there is a dispiriting slip into melodrama and a real lack of realism. It is a bizarre thing to state, but it is hard to grasp that there could have been quite so much relentless joy in the aftermath of a devastating prognosis and the way in which life had to be lived. There are only fleeting moments of depression and they are quickly washed away. Even the epilogue of archive footage of the pair and their friends, which does add credence to the chirpy perception, cannot quite justify or adequately affirm the concept that there would have been unrelenting smiling gusto at each and every turn.

One is reminded of the constant, insistent geniality of Matt Damon in Scott Ridley’s fictional The Martian, which was also guilty of such a crime. The difference here is that this is a true story. The smirking rankles and irks too because, although there is unyielding sympathy for Robin’s predicament, you cannot help but think of the class system and the privilege afforded to the upper classes. It is a depressing reminder that money creates opportunity, eases suffering and smooths out edges where possible. Some are more equal than others, indeed. That said; the achievements of Diana Cavendish are not to be underestimated. Hundreds of thousands have benefited and her legacy is guaranteed. We should all thank her for that.

The performances are decent and the direction is solid, if unspectacular. The nuts and bolts efficiency evokes the work of Clint Eastwood and Stephen Frears. Serkis has set about in an unadventurous fashion, but with a well-intended topic. The film ultimately feels limp, when it really should soar and score.