'I'm not immoral, never have been. I am amoral, that’s different,” snaps Nicholas van Hoogstraten, a stickler for accuracy (at least his own version of it). “The things the papers write about me. I’ve never threatened anyone or killed anyone — where are the bodies?” When Hoogstraten asks a direct question, accompanied by a beady stare, you often feel yourself fumbling for an answer.

Britain’s most notorious landlord, and one of its wealthiest men, “the richest man ever to stand in the dock at the Old Bailey”, he says proudly, is taking stock after getting off a 10-year prison sentence for manslaughter on appeal, only to be declared a murderer in the civil courts — where the standard of proof required is lower — just before Christmas.

We meet in a dingy hotel he owns along with seven others around Hove and Brighton. Or rather, his beefy son Rhett, 21, owns it. Hoogstraten keeps nothing in his own name. “Of course I wouldn’t think twice about having people killed, if they threatened me,” he says, “but if I was to do it, it would be done properly by professionals not obviously connected with me, it would be a professional contract killing.”

Talking to Hoogstraten, who gave himself the “van” early in his career for a spot of class, is like entering a mirror world, where all the codes of a good society are reversed, perhaps a bit like talking to a top Nazi when the war was going well for Germany.

Surrounded by a pile of legal papers, he is preoccupied by what happened to him at the Old Bailey. “I am determined to clear myself,” he says, pouring out a cup of tea without offering me one. “I am not being associated with a poxy, bungled business like that.”

The “business” was the murder of Mohammed Sabir Raja, 63, a business rival who had accused him of forgery. Hoogstraten called him “a maggot”, someone he would “break”, and on July 2, 1999, assassins Robert Knapp — a long-time associate of Hoogstraten — and David Croke turned up at Raja’s house in south London, shot him in the face and chest at close range and stabbed him five times, in front of his grandsons.

In July 2002 Hoogstraten was given a 10-year sentence at the Old Bailey for the manslaughter of Raja while Knapp and Croke got life sentences. Arrested from his extraordinary home, Hamilton Palace, a £30m copper-domed baroque mansion, the biggest private house built in the 20th century, Hoogstraten went from millionaire to lag but he says he had no problems in Belmarsh prison.

He sees himself as too much of an aristocrat of crime to be greatly affected: “I hated not seeing my girlfriends and children but I was put in with the crème de la crème,” he says, “the really dangerous people, no riff-raff.”

After an unhappy childhood in Shoreham, East Sussex, with a mother he felt despised him, Hoogstraten left school at 16 and made money from selling stamps. He is still an important philatelist. With this money he bought cheap property in the Bahamas, then freeholds with sitting tenants in Notting Hill, west London. By having no mortgages, forcing tenants out and refurbishing the properties he quickly made a fortune and became Britain’s youngest millionaire. He was a financial phenomenon, and also peculiarly deranged.

He first came to police notice in 1968, aged 23, when he was jailed for ordering thugs to throw a hand grenade into the home of the Rev Braunstein, a Jewish leader whose eldest son owed him £2,000. “He wasn’t a rabbi, he was only a cantor,” snaps Hoogstraten, irritated again. It was in jail, in Gloucestershire, that he first met Knapp, whom he calls “Uncle Bob”.

He was jailed again for eight counts of handling stolen goods and then rearrested on his release in 1972 and given a further 15 months for bribing prison officers to take him luxuries. “I ran Wormwood Scrubs when I was in there,” he says proudly. “The Home Office was very pleased with my regime too.” Perhaps so: in any case he was quickly freed on appeal. The same year, he was fined for forcible entry and conspiracy to cause damage.

In the 1980s, he entered the Guinness Book of Records for owing £5m in income tax, more than anyone else in British history, and was in court for harassing tenants, whom he referred to as “scum”. He came to public notice again when he started a vicious battle to keep ramblers off his land. In 1999 he was fined for telling a barrister representing the hikers: “You dirty bastard, in due course, you are going to have it.”

But, of course, his recent sentence was not the end of the line, and he knew it. “When I stood there in the dock at the Old Bailey, I was smiling,” he says. “I knew it was a fit-up and the case would never stand.” Sure enough, he walked free a year later when the Court of Appeal decided there had been a lack of evidence at his trial.

When he came out Raja’s family began a £6m civil action against him. He retaliated by counter- suing and infuriated one judge by refusing to divulge his assets. “I’ve got no assets at all now in the UK,” he says. “My five children got trust funds starting in 1986. They’ve got hundreds of millions.”

On Wednesday his representatives will go back to court to press the Raja family for his costs, running into millions. When I suggest he might give it a rest as he obviously doesn’t need any more money, he is astonished. “I couldn’t give a s*** myself, but there are companies and shareholders involved,” he says. “I do whatever I have to do.”

At 60 he is shabbier and a little greyer than the last time we met, some 10 years ago, and it seems at first that nothing has penetrated his malevolent shell. He is still hugely rich and still extraordinarily mean. Although we are in his hotel, I have to buy all my drinks, and as we talk he is served a lavish lunch by a pretty young Zimbabwean girl, but does not offer me a nibble. He remembers vividly that after our last interview he lent me £10. He is not quite sure that I ever paid it back (I did).

After the murder of Raja, police found teabags drying on his draining board when they searched his premises. He spends lavishly on his five children, all from different, mostly black, mothers. Rhett attended Haileybury, the top boarding school which produced Clement Attlee, the Labour prime minister, but Hoogstraten says two of his four sons, who are at Lancing college, alma mater of Sir Tim Rice and the novelist Evelyn Waugh, had to buy him a car recently because they were embarrassed at him turning up in an old BMW.

He is still attracted to power expressed through brutality. He calls Robert Mugabe “a true English gentleman,” and shows me the memorandum for a loan of $10m made to the African dictator in November, with securities reaching into trillions.

The money was officially loaned by Messina Investments, which belongs to his children. “In six months’ time, when the interest is due, it would be cheaper for them to just kill me,” he says. I agree. “I think I am more use to the government in Zimbabwe alive,” he says, chuckling for the first time.

From the arrangement he gains further wealth, access to black girls and power. He now owns large amounts of land and property in Zimbabwe. “The people would probably prefer me to be their president,” he says without irony.

He says he is involved in a lot of “charity work”, supporting rural education in Zimbabwe. This doesn’t sound convincing yet there are discernible changes in him. “I am different since I went to prison,” he says. “I am worse.”

This is Hoogstraten-speak for “better”. Being imprisoned has apparently given the man who once set the dogs on his tenants a brand-new social conscience.

He won’t admit he was traumatised but his sense of grievance has obviously wiped out other preoccupations. He is no longer even interested in Hamilton Palace, once a grandiose monument to his wealth and where he planned to be walled up with his treasures after death, like a pharaoh.

It is as if reality has cut away at some of his more narcissistic fantasies. “I don’t think like that now,” he says. “You do change your ideas with time. My children get more important to me as I get older.” Of course they are of increasing use to him as they are repositories of his wealth — walking banks — but he appears fixated on the idea of injustice to others.

So now he knows how it feels to be powerless before an indifferent judiciary. “If you are guilty you can fight to get your sentence reduced but if you are innocent, it is much harder to get anything done. I did wonder how I was ever going to prove my case.”

What he saw in Belmarsh obviously affected him deeply. Always proud to boast that he was noted by a prison psychiatrist as a possible psychopath, for once, it seems, he felt empathy with other people’s problems. He says he met many men inside who were innocent. “What can you think about forgiveness after that?” I hadn’t mentioned forgiveness, and again, it sounded odd coming from his mouth.

Taught by Jesuits, he says he is still “a believing Catholic”, and while he was in prison he took up counselling. “They sent me on a course,” he says, “they called it being ‘a Samaritan’. I was a Samaritan and I’ve got a certificate to prove it. I gave advice to prison officers worried about their emotional problems and child access. I helped other prisoners who were unjustly accused. People often come to me for advice.”

This remarkable image of him, as an agony aunt, is rather spoilt when he adds: “I am really a godfather.” He likes this idea of himself in late middle age, dispensing advice to less experienced folk, a way of feeling good about power. “People still like coming to me for advice. I am going to go on being a Samaritan,” he says. “I’ve never intimidated anyone — well, have I?”