It is another joint study, though of different lineages and kinds. More broadly, it is a rumination on Holroyd’s chosen pursuit of biography, in which he emerges as a character in his own right, alongside fellow biographers and scholars and an amateur family historian eager to uncover mysteries surrounding her paternal roots.

The central characters are two women born into the Victorian era: Eve Fairfax, an impoverished socialite who modelled for Rodin; and the wealthy author and fearsome virago Violet Trefusis. Holroyd’s accounts of their long lives (Eve was 107 when she died) occupy discrete, if occasionally interconnected, halves of the book. The main, if rather slender, connection is that Eve was betrothed (never married) to the MP and philanderer Ernest Beckett, second Lord Grimthorpe, and that Violet was Beckett’s illegitimate daughter with Alice Keppel, the future mistress of Edward VII and great-grandmother of the present duchess of Cornwall.

A more fanciful connection is provided by a grand folly of a house in Italy: the Villa Cimbrone at Ravello, overlooking the Gulf of Salerno. It was purchased and developed by Ernest Beckett – but in the wake of his breakup with Eve, so that she never got to see it, and Violet only visited once. It acts less as a setting for Holroyd’s tales of the past than as a muse for the teller: the place where his research into the Beckett family started to take off, and where, on a subsequent visit, he found and communed with other questers down these paths – the paths of the villa’s gardens and the paths to family history that they came to symbolise for him. Anyone who braves the dizzying drive up to Ravello will immediately sense the inspirational spell of the place. It has also served as muse, or refuge, for Wagner, D.H. Lawrence, E.M. Forster, Greta Garbo, and Gore Vidal. Holroyd beautifully captures the mixture of ecstasy and melancholy that generates its allure. He might strain a little to make it a unifying link in his meandering narratives, but I understand better now why, last time I visited the villa, I found myself helplessly weeping with the thrill of it all.

A gift to Eve Fairfax by Lady Diana Manners (later Cooper) of a handsomely bound empty book in which to record her life provides Holroyd with his title. He is the first to reveal in any detail how Eve filled this volume. On the surface, this was with little more than scraps of occasional verse and suchlike (many of them inscribed by her glamorous friends and visitors), with photographs interspersed here and there. From such scraps, however, a canny biographer like Holroyd is able to assemble a cast of characters and a web of stories redolent of Edith Wharton or Henry James. His remain ‘real-life’ characters, however, and he resolutely eschews any fictional embellishing of them. For all his urgings, here and elsewhere, to explore more poetic, less informational approaches to biography, Holroyd thus manages to observe one of the key constraints of ‘the biographer’s contract’, as defined by fellow-biographer Frances Spalding in her Seymour Lecture, published in ABR (February 2011).

Violet Trefusis felt freer to fictionalise Eve and her book in a late novel, Pirates at Play (1950), but it is just an incidental reference, to which Holroyd also only glancingly refers. The main ‘secret’ that he seems to want to uncover in his pages on Violet is just how good her books are as literature, obscured as these have tended to be by the reports of her appallingly bizarre outward persona. Certainly, Violet’s life, unlike Eve’s, has few secrets that we haven’t already learnt from earlier biographical portraits of her or of her youthful inamorata, Vita Sackville-West. Before he tackles the question of Violet’s works, Holroyd replays once again the dramas of the life, bringing in its previous chroniclers and another current Trefusis scholar as part of his story. The histrionics hardly bear repeating – where you lost patience long ago, you might now start losing interest – but the sidelights Holroyd provides on the psychological motivations of scholars and of what draws them to such testy, testing subjects are tantalising, not least concerning his imperatives and (if a fellow biographer) about one’s own.

Once he gets on to Violet’s writings, Holroyd manages to renew our interest with fresh, if not entirely persuasive, observations on their literary merits and enjoyments. More importantly, in a biographical study, he persuades us that her works reveal a more ‘charming and generous’, even saner, underside to her personality, which the traumas of World War II also brought momentarily to the surface. You might imagine she would have been ripe for fascism, like Unity or Diana Mitford, or have remained a complaisant expatriate in her beloved France, like several other foreign artists based there in the 1930s. Yet, faced with the prospect of the German occupation, there was no swifter English champion of the Resistance cause. On returning to her homeland for the sake of her mother and stepfather, she continued to champion it from across the Channel. This was a painful return, not least for the memories it rekindled of the much more personal trauma of her breakup with Vita after the end of World War I. Her resistances to this separation never quite stopped, and are symptomatic of the manic heedlessness that alienated almost everyone. But it is part of Holroyd’s skill that he has you thinking at the end that there is something, if not quite heroic, then deeply tragic about Violet’s excesses.

‘Make allowances for great unhappiness,’ Holroyd quotes Violet as appealing to Vita at one stage. There is an echo here of the plea inscribed in Eve Fairfax’s volume by one of her aristocratic guests: ‘Be to my virtue very kind. / Be to my faults a little blind’ – ‘a message possibly for biographers,’ Holroyd wryly observes. Both of these quotations reflect an underlying principle of his book: exasperation at the behaviour of people in the past whom we may find feckless and indulgent is perfectly justified, but it is also easy, and ultimately rather pointless. For a deeper historical and psychological understanding of them, you need to acquire a quality of empathy, a degree of identification with their times and particular situation, that is not uncritical, but also not impotently indignant.

There might be an (unintended?) message here for reviewers of biography as well – or of this biography, at least, which Holroyd himself discreetly acknowledges will be ‘my last book’. Judged by conventional professional standards, there is a good deal in its pages that you might usefully criticise in a less seasoned practitioner as faults or self-indulgences: those meanderings and longueurs to which I have already drawn attention, plus non sequiturs, self-contradictions, the occasional grammatical slackness, and the complete absence of precise documentation. For the swansong of a king (or ‘a prince among biographers’, as Spalding calls him), cataloguing such lapses seems more than useless, and rather gauche. But don’t let these detain you. It is not just a matter of ‘making allowances’ for what Violet, in another mot of hers quoted by Holroyd, calls ‘the negligently luxurious life of the British aristocracy’, or for the quirks of age and infirmity. You shouldn’t risk missing any of the beauty, poignancy – and insouciance – of the song.