Nicholas Hoogstraten's relationship with one of London's most notorious gangsters will be revealed in a new biography of the tycoon.

Documentary makers Mike Walsh and Don Jordan have followed the life of the millionaire since the Eighties, long before he was jailed for the death of a rival businessman.

Mohammed Sabir Raja was murdered by two of Hoogstraten's men, both of whom were jailed for life. In October, Hoogstraten received ten years for manslaughter.

However, Mr Walsh claims his associations with the underworld go back much further and include involvement with Tony Lawrence, a notorious East End mobster.

Mr Walsh and Mr Jordan first came across Hoogstraten in 1988 while researching a World In Action film about landlords and ended up making the film purely about him.

Mr Walsh said: "Hoogstraten had coverage in The Argus and sometimes in the Observer but he was not really a national hate figure at this time."

He arranged a meeting through Hoogstraten's former architect Anthony Browne at a top London hotel in Park Lane.

Recalling his first encounter, Mr Walsh said: "I just saw this vision coming down the stairs. He was dressed in a black tie, white shirt, black waistcoat and jacket, pinstripe trousers, slightly built-up black shoes and over all this was an ankle-length white mink coat.

"For the next one-and-a-half hours there were threats and more threats. He portrayed himself as a very nasty, very heavy man.

"But then the charm came in; sometimes he was very witty. He was a beguiling character.

"It went on for seven hours and I left exhausted and wondering if I would have the best story ever or if my legs would be broken."

By appealing to Hoogstraten's vanity, Mr Walsh said they persuaded him to be filmed for five weeks and probed him about incidents he was connected with.

These included a grenade attack on a rabbi in Brighton for which Hoogstraten was jailed for four years.

He also admitted on tape he spat at a woman and stated: "I exact retribution. I make the punishment fit the crime."

The programme was broadcast as The Dangerous World Of Nicholas van Hoogstraten.

Mr Walsh has kept in touch with Hoogstraten and said they had a love-hate relationship, without much love.

However, it was the trial and subsequent conviction of Hoogstraten for Mr Raja's killing that persuaded he and Mr Jordan to pen the book.

Through further research, they discovered links to Tony Lawrence, whom Hoogstraten called "Little Legs", and claim he supplied the grenade for the attack on the rabbi's home.

Their book, Millionaire Killer will be published by John Blake Publishing on January 23, costing £16.99.

It ends quoting letters from Hoogstraten in his cell at Belmarsh prison, insisting he will soon be free.

Mr Walsh said he was not scared but he admitted: "I do have the odd pang of worry because he is so unpredictable. He wrote to me after the trial and said I was not his favourite person."