Review: How Many Camels are There in Holland? Dementia, Ma and Me, By Phyllida Law

The title of the actress Phyllida Law's book refers to a question that dementia specialists put to their patients to help determine whether they have Alzheimer's. Law spent two years caring for her nonagenarian mother, Mego, in the tiny Scottish village of Ardentinny, with occasional help from friends, fellow villagers, and her daughters, the actresses Emma and Sophie Thompson.

Mego's memory was already failing when her husband Arthur died. She had been known to put her shoes in the oven and bacon in her sock drawer. Now she was brushing her teeth with shampoo and trying to exit a room via the window rather than the door. "Mother was lost," says Law.

The book is partly in diary form, with a scattering of watercolour sketches alongside written vignettes that veer from cheerily acerbic ("Ma has now developed a snore that sounds as if she is calling me. 'Phy ... lli ... daaaah.' So I get to be awake even when she's asleep") to more reflective and nostalgic.

Dipping in and out of her family history, Law recalls Mego's childhood as the daughter of sternly Presbyterian parents, her unhappy first marriage, the death of her son (and Law's brother) James from a head injury, and her habit of visiting her daughter at boarding school in "an embarrassing hat on loan from Penelope's". Meanwhile, doctors and community nurses come and go, as do friends with funny names (her best friend is called Mildew), and Mego's moods shift from sweetly benign to bewildered and irate.

For the most part, Law remains determinedly chirpy – sometimes a little too much so. Her and Mego's exchanges often have the ring of a daffy sitcom. At one point she shouts after her glaucoma-afflicted mother "You haven't got your long-distance glasses on," as the latter totters out the door for a stroll. "Don't worry dear," Mego shouts back. "I'm not going any distance."

Only occasionally does Law let the cheerful mask slip, and, in doing so, actually gets to the heart of life as a carer. Listening to her famously stoical mother sob, Law says: "Grief, like arsenic, stays in the system where we store all the unshed tears from long-ago life. Some things are too terrible for tears so we keep them there for later."