Somehere Towards the End, By Diana Athill

Diana Athill opens this series of reflections on extreme old age with a brace of "object lessons" in how not to think about longevity. The first comes courtesy of her friend Jean, who greets the ageing process with "resentment and despair", expects her last years to make her miserable, isn't surprised when they oh so reliably shape up, and keeps panic at bay with a "suicide kit". The second is provided by the Nobel Laureate Elias Canetti, a man much given to bouts of aphoristic self-importance, who once declared that he "rejected death". Did he mean this literally, Athill enquiries of one of the great man's former lovers? "Oh yes," she replies. The woman is "laughing at herself", Athill deduces, but at the same time "a little tremulously – I think she still felt that his attitude was heroic."

Nothing in Somewhere Towards the End – at any rate nothing that touches directly on the author herself – is in the least heroic. Its lack of self-aggrandisement, even of very much in the way of personal myth-making, is quite deliberate, and the tone of modest self-deprecation clangs in the air like so many church bells. At its heart, you feel, some way behind the view from the nonagenarian's window, lies only a question of upbringing.

Athill was born in 1917, into one of those solid, serious, upper-bourgeois families where a fuss is made about not making a fuss and the only real sins are vanity and showing off. Not surprisingly, her strongest convictions turn out to be those of sincerity, tolerance and laissez-faire, the grateful acceptance of what one has tempered by the knowledge that what one truly wants may not be procurable or even desirable.

Nowhere is this dislike of the grand gesture more marked than in the observations about sex. Bidding farewell to romantic love at the age of 43 "with a good deal of relief", she settles for a series of relationships built, one might say, on strong-minded give and take. No point, she argues, in equating understanding of the other half with approval. "Why, given our bone-deep basic need for one another, do men and women have to put so much weight on this particular, unreliable aspect of it?" As for sexual infidelity, why can't we be more like the French and regard it as perfectly acceptable "if conducted properly"? (I can think of a few reasons, but never mind.)

These principles are put undramatically into practice when long-standing boyfriend Barry's entanglement with a younger woman sets up a ménage à trois. "When Sally joined us what I felt was that now I had a lovely new friend in the house, as well as a darling old one..." Athill calmly glosses.

It was never very likely that this kind of tolerant liberal humanism would have much time for religion and, sure enough, Athill offers a brisk homily or two on humanity's irrelevance when set against the magnitude of the wider universe. ("I can't feel anything but sure that when men form ideas about God, creation, eternity, they are making no more sense in relation to what lies beyond the range of their comprehension than the cheeping of sparrows.") Such is the paralysing self-regard of the specimen life and times that this urge to see oneself sub specie aeternitatis can be a bracing experience. On the other, one can't help feeling that a certain amount of cake is being had and eaten too.

It is as if – and the feeling grows while reflections on gardening, painting and motoring yield up to out-takes from a long and exemplary career as a publisher's editor – practically no achievement can be enjoyed without its attendant satisfactions being instantly downplayed or marginalised. The art classes are a success: Athill decides that she is "about the only student in that class whose aim was to reproduce the appearance of the model". But then drawing better means working at it every day, so she gives it up. A couple of books got written in the 1960s, but "neither meant a great deal to me once they had served their purpose". The critical acclaim which greeted her memoirs Stet and Yesterday Morning, two works produced in old age, is a "treat", Sue Lawley's attentions on Desert Island Discs are highly agreeable, but "none of it mattered at the deepest level".

Didn't it? And if not, what did matter? There are two ways of responding to this exceedingly sharp and unsentimental treatise on happiness as the art of the possible. One is to congratulate Ms Athill on the balance she seems to have effected between the ferment of human existence and the checks that the average life throws in its way. The other is to wonder whether one or two basic human emotions aren't being a bit too rigorously suppressed. For myself, I rather wanted Barry's fancywoman to be chucked out into the street with her suitcase following down the stair, or at the very least for Ms A to offer a few tart remarks on her supplanter's choice of lipsticks.

Reading the final pages, where Athill contemplates the rapidly blooming (and doubtless highly symbolic) tree fern she purchased as the book was begun, I thought of the 85-year-old Anthony Powell, as recounted in his journals, lying miserably around the house swathed in a blanket "like a character in the background of a Russian novel, the old prince", commenting of his physical collapse after a prostate operation that it was "a great bore to have sunk to this state".

This is self-effacement, too, but of a rather different kind, primed by physical pain and mental anguish, but actually a kind of Romanticism by default. No doubt when it comes down to it, man is no more than a self-absorbed ant waiting to be blown off the face of the earth by an intergalactic tsunami. All the same, it is odd to find a life lived in this belief which has been quite so thoroughly domesticated.