Pat Kavanagh was a rare combination of disconcerting wide-eyed beauty, honeyed voice and incisive literary acumen.

For 40 years with the literary agents A. D. Peters (later Peters, Fraser and Dunlop) she had supervised the professional lives of an array of top writing talents — a galère that was bound to contain a variety of supercharged and sensitive egos — with a mixture of cool professional appraisal and fierce financial protectiveness.

Her skill was in the deal: her telephone negotiations, famous for their curtness and steeliness, devoid of blandishments, ensured that none of her clients — with one notorious and much discussed exception — felt that another agent could have delivered them a better deal. It was an eloquent testimonial to her authors’ devotion that when she and fellow agents broke away from PFD last year to form a new agency, United Agents, all her names stayed with her.

Patricia Kavanagh was born in Durban in 1940, the eldest daughter of Chris Kavanagh — a journalist and war hero who wrote a book, Timid Eagle, about the war, and another about running an ostrich farm — and a mother who was a health inspector. Her parents separated when she was a child, and she always felt conscious of being the only child in her school with divorced parents, who did not have any black servants.

At the University of Cape Town — where her striking glamour and Veronica Lake hairstyle made her the cynosure of all eyes in the Rag Queen contest — she met Prue Leith, her future client. Determined to make a career as an actress, she appealed to Leith’s mother, Margaret Inglis, the foremost actress in South Africa at the time, to give her an audition at her home. Inglis told her to imagine she was a mother who had just lost her baby, and Kavanagh’s anguished cries earned her a job with a theatre troupe travelling to Rhodesia.

In the world of the stage, she found she attracted both men and women, and when she made her way to London in 1964, she enjoyed a brief moment on screen, in the arms of Richard Burton in Andrew Sinclair’s film of Under Milk Wood. About this she said: “I never got paid — but I did get to snog Richard Burton.”

As a copywriter with the J. Walter Thompson agency she wrote neat slogans (one was for lard: “It’s as easy as Spry”) but she was never confident of her own writing talent. Answering an ad in the New Statesman for a literary agent, she met A. D. Peters himself, and said she learnt everything from him. “The great secret of negotiation,” he told her, “is silence.”

She would hear him mention a price on the telephone: if the caller demurred or expostulated, he would merely let a long pause hang in the air, after which he would secure his original deal, without concession.

This ploy suited her nature, which was to be concise with words. Her authors often agreed that they had never known such brief telephone exchanges, or correspondence, as they had with Kavanagh: no pleasantries, it was strictly down to business. If authors and publishers alike were a bit afraid of her, there also seemed to be an expectation that they should be afraid. She was the antithesis of the nurturing or nannying agent: she did not ring to ask how a book was going, or make consoling suggestions, or soft-soap her authors. Instead she would calmly await delivery and then show absolutely no disposition to praise a work that did not meet her standards. Authors who in her view were content to write rubbish were quietly consigned to other partners.

Though most clients became personal friends, she would say that she expected her authors to be adults, and that hand-holding was not part of her work. She would never represent someone whose work she did not admire. But enthusiastically telling someone their idea was wonderful was not in her nature. When Allison Pearson outlined her novel, I Don’t Know How She Does It, Kavanagh listened carefully and said: “Yes . . . . But of course it will have to be very well written.”

She regarded her role, she said, as that of a family doctor or a country solicitor, who kept her clients’ professional secrets as she expected them to keep hers. She did not see literary agents as public figures, hated the rise of the celebrity agent, and would urge authors for whom she had secured generous sums — including Joanna Trollope, Clive James, Ruth Rendell, James Fenton, Robert Harris, Andrew Motion, Francis Wheen, Blake Morrison and Margaret Drabble — not to talk about it publicly.

One of the many friendships she formed was with the great American humorist S. J. Perelman. When Perelman heard from Harold Evans that Kavanagh was now “in a state of holy matrimony” withthe then unknown Julian Barnes, he wrote, a fortnight before he died: “What a surprise! And how becoming I’m sure it must be! I’m only sorry I’m not there to kiss the bride and wish her everything wonderful. As for your legion of admirers over here, I speak for all of them, I know, when I say that if the groom harms one hair on your head or blacks one of your eyes or so much as knocks you down even once, why the whole lot of us will rush over and deal with the blackguard as he deserves. Let him put that in his pipe and smoke it.”