For those who have followed the Melrose family saga of Edward St Aubyn's fiction, this counts as a very sad moment: the author is killing off the semi-autobiographical series he began writing 22 years ago, a story so close to the bone that St Aubyn was still in recovery from multiple harrowing causes as he wrote the first sentence. The scion of Cornish landowning gentry and an American dynasty, St Aubyn was abused by his father, Roger St Aubyn, as a child, and fell into heroin use in his teens.
Swaddled in a bath towel and sweating profusely from the emotions that the writing inspired, he scratched out his shocking, darkly satirical debut, Never Mind (1992). It dramatised a childhood devastated by sexual abuse from the age of five, and spawned four further instalments as the life story continued into teen years eaten up by drug addiction and an adult wilderness filled with the detritus of a failed marriage, disinheritance and psychoses.
I wonder, though, if St Aubyn's psychotherapist were still around today - the one who 22 years ago suggested that St Aubyn unleash his demons in fictive form, he tells me, as he burrows further into a large, leather analysand's chair in his Holland Park home - whether he might consider the Melroses' demise a happy ending.
The final Melrose novel, At Last (Picador, £16.99), is a set-piece in which St Aubyn buries his fictive mother, Eleanor, who has disinherited her son - the author's alter-ego, Patrick Melrose - leaving her wealth to a New Age guru (St Aubyn's late mother is believed to have done something similar).
Like almost all of his tightly structured novels, this one covers the four-hour span of Eleanor's funeral, the end of which appears - finally - to set the perpetually unhappy Patrick free, after he realises how much of a passive collaborator she has been with his abusive late father. It is filled with the savage social satire, existentialist rumination and rich interior monologues for which the author is known, head-hopping its stream-of-consciousness narrative from Patrick to his young sons to elderly blue-bloods to his stoical ex-wife, and back again.
David Melrose, the fictive father, died three books ago in Bad News (1992). Now, with the disposal of this last piece of parental baggage, Patrick's psychic liberation is summed up not just in the glibly euphoric title – at last – but in his reflections on orphanhood: "He seemed to have been waiting all his life for this sense of completeness."
For St Aubyn, the end of the five-part family psycho-drama is part liberation, part loss and, I imagine, part terror too. He concurs. "The first sentence of the first novel was written in October 1988, and the last one of the fifth one was written in October 2010. So it's a fictional world I have been living in for a very long time.
"I'm experiencing a mixture of relief at concluding the story, and also loss at having to part with the characters. It is sometimes intimidating, when I think it may be unlikely to produce something as rich [again], though that's just my anxiety."
Eleanor's death, though, cannot simplistically be equated with personal exorcism, he says. The fiction has gained too much momentum over the years for it to rely on the exhumation of personal history alone. By the point he was writing this last Melrose book, he was entirely immersed in an imaginative process.
"There's a spectrum of characters who are uninvented - Patrick and his family are portraits. Certainly my feelings about the death of my parents are in the Melrose novels, but there are various differences between the first three books and the last two. The first three referred to a body of facts related to my characters, and to my addiction, while At Last is dealing with elements made out of the previous novels."
By the time St Aubyn began writing the Melrose drama, he had already had three false starts with novels abandoned through his twenties. The debut, once complete, set him on course and led to due critical success: a Booker nomination (and a subsequent furore after the clear favourite, Mother's Milk, didn't win), a cult following and acclaim for subject matter that imaginatively splices upper-class ennui with class-A drugs, and a prose style that supposedly crosses Evelyn Waugh with Bret Easton Ellis, although it would have to be Waugh on acid and Ellis in Eton College tails.
Yet his salvation was also his curse. The autobiographical aspects of the Melrose drama have plagued him ever since he spoke publicly about his rape by his father. Critics have tried to pin down the fiction-versus-autobiography quotient in his books. The fuzzy boundary between his life and art has led to confusions between the writer and the alabaster-faced aristocrat of his fiction.
As it turns out, St Aubyn emerges at the door of his characterful home ruddy-faced, relaxed, and with none of the reputed hauteur. He leads me to a room resembling a therapist's sanctum – his leather seat, my high-backed inquisitor's chair – and answers with slow, selective sentences. One imagines, maybe wrongly, that a wordy undercurrent is rolling internally, just as it does with his outwardly cool characters. He also deals in some well-rehearsed sentences that he has repeated, probably for as long as he has been asked about the life-versus-art conundrum of the Melrose series.
For someone whose satire is in part angled at aristocratic inheritence, St Aubyn is unwilling to make any final, damning statements. When pushed on how red his blue-blood might be, he is clearly reluctant to take an ideological stance. He does not disapprove of inherited wealth per se, but does point out the fact that neither parent worked, and did nothing to help the abuse suffered in childhood.
Family dysfunction is not just endemic to the landed classes, he adds, although the vacuum that the lack of necessary employment leaves could become potentially destablising. "Freud said it was love and work that made us sane. This is a world where everyone is insane. The elite are not thriving in these novels. But there is suffering everywhere.
"Certainly the novels are a critique of privilege and inherited wealth. It's not the dream we should be sacrificing our lives to. He [Patrick] has seen at close quarters that privilege is not a privilege at all." As he has himself? "It was not the privilege that struck me in my early life," he answers, wryly.
But the heart of St Aubyn's fiction rises above questions of class conditioning to reflect on the universal themes of identity and freedom. "I have never met anybody in my entire life who is not interested in how they became how they are, whether they had a choice in the matter and whether they can become free [of the conditioning]. This is essentially a human concern and it's a driving force behind all the stories."
One of St Aubyn's strongest features has always been his ability to deal in multiple inner voices. In Mother's Milk, he even dared to dramatise the inner monologue of a newborn baby as he slid out of his mother's diluvial fluids and into the world. Creating a voice on the page has never been a problem, he says. Finding an authentic one in real life was harder.
Mimicry became compulsive for him while he was growing up. In Some Hope (1994), different voices take over Patrick's mind, like aural hallucinations. The experience closely resembles his own. "I hardly spoke in my voice. I adopted others."
It was different with the written word. By the time he wrote his debut, the struggle to find a voice had already taken place with the earlier abandoned novels, and some comedy sketch writing for radio.
While the Melroses are fading from St Aubyn's imaginative life, he will still be dealing with their ghosts for the foreseeable future. This book, as well as a film adaptation of Mother's Milk, starring Jack Davenport and Diana Quick (for which he has co-written the screenplay), is in post-production and it will hopefully introduce the family to those who have never heard of the Melroses. It is, in fact, surprising that adaptations have not been made earlier, given the film industry's love of the country house saga, although there have been inquires along the way; Richard E Grant recently expressed a keen, though unrealised, interest in making a film of Some Hope.
Now, for St Aubyn's inner task-master, there is the job of fending off any latent anxiety of not working, and just enjoying the considerable achievement. "I am completely blank. I'm not protecting some marvellous idea. I'm having a book published, with a new film on the way, and I don't need to persecute myself for not having started a new novel, although that would be typical of me."
Putting the Melroses away will take some time, but then there is the curious historical disclaimer, which has seen family members creep back tenaciously into his mind, like barnacles clutching at the walls of his imagination, even as he has resolved to put them away.
He tried to end the series when Some Hope was written - after which he wrote two non-Melrose books: On the Edge (1999) about New Ageism in California, and A Clue to the Exit (2000) about a screenwriter who is given six months to live.
But then Mother's Milk emerged a few years later, in 2006, just as he thought he had turned the corner. "I thought I had finished with them twice before so I'm the worst person to ask [if there will be another instalment]. Somehow they insisted on coming back. I can't be sure they won't come back again. All I can say is that there is no intention to return to the family.
"Whether Patrick proves to be an irresistible character in an age of recycling," he says, with a smile, is another question. He may even come back happy, although St Aubyn has quipped that this new mindset could take rather a lot of research. Either way, letting him go is, for now, an unknown.
"He could be brought back to make a guest appearance in a future novel. We might find him sitting next to someone on a plane. Anything is possible."