This year sees the centenary of Oxford’s Iris Murdoch, one of the greatest novelists of the 20th century, and also the 20th anniversary of her death, which attracted worldwide attention owing, in part, to her well-publicised five-year descent into darkness that preceded it.

That this was well-publicised arose in large part from the decision of Prof John Bayley, her husband of more than 40 years, to reveal all the distressing consequences of her Alzheimer’s disease in his 1998 book Iris: A Memoir of Iris Murdoch.

It was at the time of the publication of this that the main picture on this page was printed to accompany an interview with Bayley, in the couple’s notoriously chaotic home in Charlbury Road, by my colleague Reg Little.

In the course of this, Dame Iris went missing. “I am afraid I did not lock the door when you arrived,” Bayley told Reg. A frantic search of the streets followed. She was found in the guardianship of a neighbour, in tears.

During the interview, Reg alluded to Bayley’s revelation of intimate details of the sex life of his wife, “this most private of women”, and put it to him that “if she could, his silent wife would scream in protest”.

The professor seemed to agree. “When you get involved in this situation, you feel that the person concerned doesn’t bother any more. I certainly wouldn’t have dreamed of writing about her in the old days. She would never have wanted it, but that just doesn’t matter.

“She knows, roughly speaking, what I have done and she is happy about it.”

But the book, and two volumes of further reminiscence, greatly upset some of her friends.

The novelist and biographer A.N. Wilson led the attack during Bayley’s lifetime in Iris Murdoch as I Knew Her (Hutchinson).

He wrote: “I had always thought of him as dear, sweet, bumbling, smiling JOB, who ‘didn’t mind a bit’ when IM received all the plaudits, achieved international fame as a writer of genius, took many lovers and then declined into being a demanding, incontinent old wreck.

“I changed my view and began to wonder whether, inside the uncomplaining little leprechaun, there was a screaming, hate-filled child who minded very much indeed.”

Now the opinion of Murdoch’s authorised biographer (and former carer) Peter J. Conradi has been delivered in his new book Family Business: A Memoir (Seren, £17.99).

Feeling freer to comment after Bayley’s death (in 2015), he accuses him of being “addicted to the oxygen of publicity”.

Conradi writes: “John’s exposure in his three memoirs of Iris in her last illness made him enemies. Together with the film that followed [with Kate Winslet and Judi Dench as Murdoch], they ensured that Iris is nowadays remembered not only for her novels and her brave pioneering philosophy but for her love-life and final illness.

“The first memoir . . . seemed to be an act of appropriation and a seeing off of rivals for her affection.

“There were tears and heated rows when John left papers lying around the house in Wales [that of Conradi and his partner] that made clear a second – then a third – memoir was on the way and we confronted him. ‘I don’t see why I should be silent,’ he once said.

“In 1998 [Iris] wandered unscripted on to live camera in Charlbury Road, dishevelled and distraught – and thus onto the 9 o’clock ITV news. The affront, grief and fear this caused marked a nadir.

“Taking Iris out to parties at a stage in her illness when this distressed her caused further bewilderment.”

Bayley’s taking his wife to the launch party for the first memoir, at Blackwell’s in Oxford, was “gratuitous and unkind”.

It was quite clear to me that parties were no longer Iris’s thing a good few years before that, when I observed her, vague and wandering, among guests at a friends’ wedding.

This was, I think, my last sighting of her ‘in the flesh’.

My first came in 1972 at the Cambridge Arts Theatre on the opening night of her play The Three Arrows, a drama set in medieval Japan starring Ian McKellen. It was not a success.

In 1975, by then employed by The Oxford Times, I attended a poetry reading she gave in aid of Amnesty at the University Church. I maintain a vivid mental picture of her crossing Radcliffe Square after the event, a tiny figure in a duffel coat, clutching a preposterously large bouquet to her bosom.

Two years later we were both guests at a big party at St Catherine’s College, marking the publication of The Fontana Dictionary of Modern Thought by its Master, Lord Bullock. She was hoovering the red wine almost as quickly as the notoriously bibulous historian Richard Cobb.

In 1980 we found ourselves among the gawping crowd when Andy Warhol partied at Raymond Carr’s home in Charlbury Road, near the Bayleys’ later residence.

I wondered if this would figure in her fiction one day, but it never did.