Xavier Alford is 42. Married to Anna with two children, a girl and a boy, he is a successful documentary-maker. Athletic, fit, handsome and thoroughly competent, he seems to have everything he could want in life. Then he is struck by a comparatively rare neurological complaint, multifocal motor neuropathy, often known as Guillain-Barré syndrome. This neuropathy is a devastating condition. At its most developed it will leave the sufferer with a fully functioning brain but no bodily responses at all. We see one patient in that situation, in which he can only indicate “Yes” or “No” by blinking his eyelid, and even that function eventually goes. This is the “locked in” syndrome to which the title refers.

We see Xavier with great bravery travel the country meeting other sufferers such as “Scotty” and Winston, a woman and the “locked in” man, surveying what could be his condition 10 years from now. At the moment, he is reasonably fit, can do most things, including driving a car, but must visit a hospital every three weeks to get a blood plasma transfusion, which helps to delay the onset of the severity of his condition. It helps but, even this, can give him blinding headaches and some days he is just too tired and remains in bed.

This is an honest, professional and intensely moving piece of filmmaking. having looked after a partner for 11 years with multiple sclerosis, it brought many memories flooding back, especially the painful ones. The two conditions lot in common: the continuing degeneration of the body and the infuriating way it makes the most simple things, such as picking up a cup of coffee, a challenge.

The most moving moment in this film, and one very redolent of my own memories, is when patient “locked in” has to be told by his wife that treatment may soon have to be ended. He understands perfectly what is being said to him and can do nothing physically, yet the grief and concentration in his eyes say a lot.

Xavier made this film, partly to confront his own feelings and those of his family about what has befallen him. The children take things mostly in their stride, although his son Louis admits he is sad when his father loses his temper over things he cannot do. He gets them to ask him questions about his condition. His wife Anna, being a more reflective adult, is a rather different case. She often refuses to co-operate in certain scenes and she tends to be a fleeting presence in the background. At times, she seems rather mean to him, even blaming him. Their marriage seems to be fraying. Disability is not part of the deal when you marry or enter into a permanent relationship with someone. It is neither hoped for nor expected. It opens up to both Anna and Xavier years of suffering and that is a formidable prospect.

This brings us to a final subject that is not spoken about directly and yet hovers over the whole film – suffering. The peculiar problem hanging over Xavier and Anna and their children’s lives in the future is suffering. Suffering has no cure. There is no blame and there is no respite. That is – unless medical science comes to the rescue – is the predicament of Xavier. My own experience of suffering is that if it cannot be avoided, it must be undertaken with full knowledge and full acceptance. I wish Xavier and his family well.

Locked In: Breaking the Silence is out on BFI Player and BBC4 on Monday, November 30th.