Mortimer smarts at book's claims he was Rumpy-Pumpy of the Bailey

Stories of spanking and serial affairs in unofficial biography embarrass creator of Rumpole. By Andrew Johnson

"Oh God," he said, on learning that the book will expose salacious details of his private life, including claims that he liked to spank and be spanked. "But what can I do? I can't stop it. It's a rather unpleasant book."

Leaked details of The Devil's Advocate, which is published this week, have already revealed that Mortimer, a talented lawyer as well as novelist, dramatist and TV and radio writer, had an illegitimate child with the actress Wendy Craig 40 years ago. And there is more to come. Written by Graham Lord, the former literary editor of the Sunday Express, the unauthorised biography is an account of Mortimer's sex life and difficult marriage.

Complaining that the book was filled with "half-truths", he said he was horrified and would refuse to read it.

"Graham Lord told me he was going to write the book, and then told the publishers that it was authorised. So we said we didn't want people to talk to him. It's very upsetting."

Mortimer's friends and family refused to co-operate, leaving Lord to rely on the testimony of enemies, former friends and newspaper clippings. Those who remain close to Mortimer, such as the writer Kathy Lette, are also criticised by Lord. But when he defended the producers of Oz magazine in 1971, Mortimer argued that anybody should be able to publish anything in the interests of free speech.

Mortimer is known to the public as a brilliant figure who, aside from his work as a judge and QC, wrote the Rumpole series, the script for the classic television series The Jewel in the Crown and numerous books and plays.

But Lord paints a very different picture, portraying him in The Devil's Advocate as a ruthless charmer and egotist who treated his first wife Penelope cruelly for the 22 years of their marriage during which he is said to have had numerous affairs. It is also claimed that he embellished many of the stories of his triumphs.

Acquaintance after acquaintance is lined up to dish the dirt, including former lovers. Molly Parkin, a fashion editor and painter, and the actress Shirley Ann Field both said they had affairs with Mortimer - and both claimed that he liked to be spanked.

Field, who, the book alleges, was 26 when she had her affair with Mortimer, is quoted as saying: "He was fun, enormously charming, and made me feel so special and safe. However, he had this thing about spanking with hairbrushes. I thought, God, what a strange one we've got here. I just thought the spanking was a public school sort of thing."

An unnamed television producer is quoted as saying: "John's an awful shit pretending to be a nice guy. He's ambitious, absolutely ruthless and has a huge ego."

Lord describes an 80th birthday party for Mortimer given by Kathy Lette. He writes: "[She] risked over-exciting him by taking him to a restaurant in Covent Garden, School Dinners, where the waitresses were dressed in skimpy schoolgirl tunics. To stimulate him beyond endurance she took him also to another 'erotic' London venue, Club RUB, which should be 'huge fun', she twittered. 'It's all quite naughty and they whip you with lettuce and things'. Lettuce? What, no hairbrush?"

Lord then says that Wendy Craig threatened him with legal action for invasion of privacy if he published the story about her son with Mortimer. The boy was born in 1961.

He adds: "He [Mortimer] spiked my guns by confessing all to the The Sunday Telegraph, but Wendy Craig was not a party to the decision to go public."

Lord does concede that Mortimer's "close friends, however, are unswerving in their admiration". "'We all adore him,' said Lette. 'He's just God's gift to womankind.' On another occasion she said Mortimer was 'a total babe magnet'."

Mortimer said yesterday that he was dismayed that the book will be serialised, and said that an authorised biography by The Times columnist Valerie Grove, to be published by Penguin next year, would set the record straight.

He also claimed that Lord had not been completely honest with the sources of some of his information, citing a critical quote by the thriller writer Frederick Forsyth which appeared in an article written by Lord in last week's Mail on Sunday. But Mortimer, now 82, told The Independent on Sunday yesterday: "Freddie wrote to me and said he had never spoken to Lord."

He added: "I'm not going to read the book. He [Lord] is very angry with us because we told people not to speak to him."

In the biography, however, Lord writes: "When I asked John about writing his biography he encouraged me to do it and agreed to co-operate. I sent my publisher a proposal for what I called an authorised biography. The project began to collapse when Mortimer's literary agent demanded to see a copy of the proposal and accused me, aggressively, of lying because I had called the book 'authorised'.

"Ironically, Mortimer did me a huge favour because his devious behaviour showed me an unattractive side of his character."