Five-minute Memoir: How my mother, the sculptress, coped with Alzheimer's

My mother, Faith Tolkien, was a sculptress. She could catch the essence of a person in her portrait busts – the elusive individuality that marks each human face out from all the billions of other faces that there have ever been or ever will be.

And then one year the talent left her. She struggled for months with a portrait head but it was useless. She could not capture a likeness. Alzheimer's had arrived, moving slowly and stealthily, picking its way through her cerebral cortex like a mountaineer finding footholds in high places.

My mother was in denial and so was I, afraid to face up to a responsibility that I did not know how to handle. She called her problem short-term memory loss and started to write everything down in pocket diaries which she promptly lost. She couldn't sleep and ironed and re-ironed laundry through the long watches of the night.

But my mother, the artist, adapted to her new circumstances. She made no more portraits but instead worked from her imagination, sculpting a statue of the baby Jesus held by his father. At St Joseph's feet the tools of his trade, a hammer and nails, lie discarded as he cradles his tiny son. But they are there for a reason, pointing towards the child's future martyrdom, nailed to the cross. The father gazes with exquisite tenderness at his son and it is as if he senses the inevitability of what is to come.

After St Joseph, my mother began work on her last commission, a statue of St Leonard, the patron saint of prisoners, for her local church, St Leonard's in Watlington. But Alzheimer's now held her prisoner and she could not finish the statue. Instead, she began to dismantle the saint's hands and then his arms, expressing through her art the extinction of her talent, until finally she gave up.

The statue was covered in a dirty cloth while all around, her studio filled up with cobwebs, smelling of dust and neglect. These were hard times. She was fearful and she wandered. Over and over again she made me promise never to take her out of her home. I did so, telling myself that I would never let it happen as long as she knew where she was. And yet as she deteriorated I didn't know whether I would be able to keep my word.

But through all the anxiety and all the confusion she never lost the love in her heart. One of her carers told me that she'd arrived at the house one afternoon to find my mother cradling the head of me that she had made 12 years earlier, whispering into my green, resin, bronze ears. She knew that her sculptures contained life, even if she could no longer create them.

My mother's memory for the recent past began to disappear, draining away like wine from a glass. She forgot my childhood and it was as if I was losing it, too. The walls of the cottage where she had brought me up alone after my parents' divorce were shrinking inwards. Soon she was left only with her own earliest memories – staying up late on summer evenings in her bedroom to watch men in white flannels playing cricket on the green below her window; running to meet her father at the end of the street when he came home from work; her dog and cat lying curled up together on her invalid mother's bed.

I decided to enlist a photographer friend's help to make a book of my mother's sculpture. This was something she had always wanted. But time was running out – my mother was rapidly losing her capacity for abstract thought and I was worried that she would be unable to understand the concept that there was going to be a record of her life's work.

A sculptor friend repaired the hands and arms of St Leonard and the Bishop of Oxford came to unveil the statue. I sat beside my mother at this, her last public event. The Bishop gave an address. He said that the statue, like the church, will last long after we are all gone and forgotten. It points towards the timeless and the eternal; towards God, and I thought at that moment that he could have been speaking about all of my mother's work. I felt more proud of her than I had ever felt before.

The years that followed were not easy. I was constantly frightened for her but in the end I was able to keep my promise. When she finally left her cottage she didn't know she was leaving. She took with her a few personal possessions and her sculpture book. And later that year in the nursing home she ran her hands over the pages and looked up at me and said: "It's mine. I did it". "Yes," I said. "You did."

'Orders From Berlin', by Simon Tolkien (Harper Fiction) is out now in hardback