It had always endeared me to John that, as an excitable youth of 24, he fell in love with a mother of four aged 28. The beautiful Penelope Dimont, née Fletcher, already had two daughters by her husband, Charles Dimont, another by her wartime lover, Kenneth Harrison, and she was now pregnant with a fourth daughter by her latest lover, Randall Swingler. (A man had only to hang his trousers over the end of the bed, as Penelope said, for her to become pregnant.)

When they married in 1947, both were about to publish their first novels, and she was the next important influence on his life. The media became obsessed by the writing pair and their large brood (six children by 1955) living in Hampstead in chaotic domesticity.

Life was turbulent, punctuated by dramatic rows and reconciliations, usually caused by the “hints and confessions, implausible excuses, furtive mutterings on the phone” during John’s forays into the theatre, “which supplied a succession of accessible girlfriends”, as Penelope, an inveterate diarist, wrote.

Both plundered their marriage in their work. John’s 1973 play Collaborators was his version. But in 1962, Penelope’s The Pumpkin Eater dissected their life with an unsparing honesty.

Later filmed with a script by Harold Pinter, it told the story of a screenwriter husband’s affair with an actress, and the actress’s pregnancy coinciding with his wife’s abortion and sterilisation.

In real life, John’s affair with the actress Wendy Craig, star of his latest West End play, produced a son, just after Penelope had been aborted and sterilised. It was not until their marriage was long over and he was happily married to “Penny Two”, with two more daughters, that he met, at the age of 82, Ross, his 42-year-old son by Wendy.

Given John’s elisions and excisions as a memoirist, it was fortuitous for me that an unauthorised biography appeared two years ago. Graham Lord’s inquiries caused Wendy Craig to contact her former lover in 2004, and John to go public on the welcome discovery of this likeable son who so resembled him, and of whose existence he claimed to be unaware.

By now John was adept at self-deception, erasing unpleasant or inconvenient matters from his mind.

“When John doesn’t want to know something,” the forthright Penny told me, “he doesn’t know it.” As one commentator said at the time, if a footballer was caught cheating on his wife he would be labelled a love-rat. John, national treasure, escaped censure. But in several works he had already written about a son whose paternity is in dispute; in Felix and the Underworldhis writer protagonist is accused of fathering a love-child, causing headlines and publicity that revitalise his flagging reputation. (This proved highly prescient.) Ross grew up believing he was the son of Wendy’s husband Jack Bentley. His mother said that Bentley, on his deathbed in 1994, had implored her never to speak about it. So it was not until September 2004 that Wendy went to lunch with John and Penny.

Ross did not wish to intrude on their lives, said Wendy; but they urged otherwise and things moved swiftly. Ross telephoned John, and told Penny: “Penny, do you realise I’ve spoken to my father for the first time in my life.” When he arrived at Turville Heath Cottage, Penny greeted him – “Welcome to the family” – and led him into John’s study, where the two exchanged a manly British handshake.

Ross spied a signed photo of Fred Astaire, given to John by his daughter Emily, and said: “I have an album of Stacey Kent singing Fred Astaire songs. I was listening to it before I came. John pressed the play button of his stereo – and he had the same CD on!” Photographs of Ross taken that day revealed that he looked more like his father than any of John’s other children.

© Valerie Grove 2007

Extracted from A Voyage Around John Mortimer, to be published by Penguin on October 25 at £25.

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