Celebrity interviews tend to be preceded by a courteous email exchange between publicist and journalist, one politely begging the other to play ball. But Jonathan King – singer-songwriter, pop impresario, lifetime holder of a spot on the sex offender's register – cuts out the middlemen with a letter to the editor.

"You might be interested to see that my autobiography was last week No 1 on the Amazon Kindle pop culture chart," he writes. "My YouTube videos have literally millions of views... Yet I'm still airbrushed out of the BBC Stalinist revision of history; the chart shows have been instructed not to play my music!... I think at least an interview with me would be fascinating copy."

Since his conviction for child sex offences in 2001, and his release after three-and-a-half years served, King has been ignored by the media. There was a flurry of interest when he emerged, grinning and giving a double thumbs-up, from Maidstone Prison in March 2005. And then, nothing.

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These days, when he writes to the letters pages under his own name, his views are never published. When he writes under a pseudonym, he claims, they are printed almost without fail.

Earlier this year, he was cut from the BBC's re-run of an old edition of Top of the Pops. Under the name 100 Ton and a Feather, King reached the Top 10 in 1976 with a version of "It Only Takes a Minute". When the BBC edited out his performance last April, King wrote to the director general, Mark Thompson, to complain. "I know Mark," he says. "I know everybody. He was a junior producer in America when I was presenting Entertainment USA , which was the No 1 show on BBC2 at the time, with 9.7 million viewers."

Unexpectedly, Thompson replied with a full apology. "I put his email on my website, which gets 10,000 hits per day," says King, "and the Daily Mail printed it in full. The Mail must have been thinking, 'Who do we loathe most? Vile pervert King, or the BBC?'!" After this rare attention, he goes on, "I saw a door opening. I wrote to various newspaper editors and said, 'I'm still around. I have a lot of happy memories and experiences. How about lifting the ban?'"

At his suggestion, we meet in the tea room of the Royal Lancaster Hotel. I suppose I expect him to be haggard, haunted, beaten. But King is 67 in December and, as he declares proudly, looks some years younger. He says he swims for five hours per day when he's abroad during the summer. (He can't use public pools in the UK, "for obvious reasons".) Perhaps he's aged better than his peers because drink and drugs were never his preferred vices.

It soon becomes clear that he does, indeed, know everybody. Among the names dropped during our interview are Jonathan Ross, whose first job was as King's junior researcher; Dave Gilmour, of Pink Floyd, whose first band, Joker's Wild, King produced at Cambridge; Peter Cook, who knew all the lyrics to King's B-sides; Simon Cowell, who put up £50,000 of King's £150,000 bail when he was arrested in 2000; Stephen Fry, with whom King had a raucous lunch at Le Gavroche just the other day. He claims to have been the first to play Jimi Hendrix a version of "Hey Joe", and to have suggested that Hendrix record a cover version. He met Rupert Murdoch on Concorde 30 years ago, when King was still writing a column for The Sun: "Best thing in the fucking paper," Murdoch told him, apparently. By the by, King flew on Concorde 256 times: "That's more than David Frost!"

King is a chronic networker. By his estimate, he suffers "negative reactions" in public about once a year. "I have lots of friends," he says. "I mix with all sorts of people, of all generations." Does he have a love-life? "Only with myself! You get older, and your desires slacken off. You can't fall in love after 40; you know so much about life that you can't get fooled anymore."

He still lives in the Bayswater mews house that he bought for less than £19,000 with the royalties from his first hit, 1965's "Everyone's Gone to the Moon", recorded while he was a Cambridge undergraduate. He makes money from his music publishing company, which holds the rights to the Abba and Genesis back catalogues. "I earn about £10,000 a month on iTunes," he explains, "which isn't much compared to the good old days when I sold millions of records. But I suppose some people would consider 120 grand a year not a bad annual salary."

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He would like to be more involved in the mainstream media, but has instead spent the years since his release self-producing feature films and LPs, and self-publishing books. His first micro-budget 90-minute film, Vile Pervert, is a fictionalised version of his trial, in which he presents his side of the story. King plays all the characters himself. It begins with a full-frontal nude shot, and has had 64,000 full views and downloads. His new film, Me Me Me, is "coming up for 11,000". He makes no money from the films; the books (his autobiography, 65 My Life So Far, and a novel published under the pseudonym "Rex Kenny") cover their costs.

If his musical oeuvre was thought of not as naff, catchy pop, but as great art, then it's possible King would be more acceptable to polite society, like Roman Polanski. "I might be thought of as an eccentric artiste," he agrees. Then again, he tells me, there's a society in Germany which gets together every few weeks to watch Vile Pervert. "They consider it a work of art... A friend of mine said it should be in the Turner Prize."

Critics may have ignored his creative output but, he insists, "The last 10 years have been probably the most fun I've ever had in my life. My worst decade was my forties. I had hits, but I was bored to tears. Suddenly [the arrest, trial and imprisonment] happened and I was faced with a choice: go into gentle retirement, slash my wrists or do whatever people who give up do – or regard it as a challenge."

He always hated the thought of being popular. "I've always liked people who know me to like me, because I think I'm quite likeable. But people who make up their minds based on the image in the papers or a voice on a pop record? They're idiots. I've always gone out of my way to alienate the masses. And you can't get more successful at it than being considered a child molester, can you?"

Even as a boy, King says, he would "determinedly irritate and annoy everybody." Brought up in Surrey, he went to boarding school at Charterhouse, where his first love was literature, music his second. By the time he was 15, he knew he was bisexual.

"I watched the Dirk Bogarde film, Victim, and there were people going to prison because they happened to fancy people of the same gender. I thought 'Oh my God, this is what's going to happen to me!' I was horrified. Then I went to a same-sex school and all these extremely good-looking 16 and 17-year-olds were only too delighted to have a bit of fun. I thought, 'Why not indulge?'"

During his pre-arrest career, King sold 40 million records under various guises. "Everyone's Gone to the Moon" was covered by Marlene Dietrich, Nina Simone, Frank Sinatra, Bette Midler. He discovered Genesis. He ran Decca Records. He wrote newspaper columns and hosted televsion and radio shows. He rebooted the Brit Awards. Erasing him from pop history is no mean task. Just before he was arrested, he claims, he was offered the chairmanship of EMI.

By his own account, prison did little to dampen his enthusiasm. His first stop was HMP Belmarsh.

"When I left, all the officers said 'Jonathan, we're really sad to see you go. You made this prison a much happier place.'" Then he was sent to Maidstone, where he claims to have had a "brilliant time".

He still writes a column for the prison magazine Inside Times. "I wish people like Ken Clarke or David Cameron would bother to say 'Jonathan, you spent three-and-a-half years in prison. Can you come and talk to us about what works, what doesn't work , what we should and shouldn't be doing ?' But they're all too scared of the media."

And so to his conviction, albeit in the reductive newspaper fashion that he abhors. King was sentenced to seven years for sexual assaults on five teenage boys during the 1980s, though he was accused of a pattern of similar offences stretching back to the 1960s. His accusers, now grown men, said he scarred them emotionally for life. Most had submitted to King's attentions on multiple occasions. The details have been reported more comprehensively elsewhere, but King's defence rested partly on the men having been 16 or 17 at the time, not 14 or 15, as they claimed.

He doesn't believe his conviction will be quashed, though he continues to appeal, and has spent about £1m on legal fees. He insists no crime took place – but also suggests that, well, everyone was at it back then. "Morality changes," he says. "The law changes. Until I was in my twenties, any kind of gay contact was illegal. It's wrong to judge the morality of then by the morality of now."

If he's guilty, then he has done his time (or half of it). If he's not guilty – or, at least, not of anything criminal – then his actions were surely immoral. Does he regret it? "I wish I'd had the wisdom then, that I have now, to think of the consequences... I've never in my life had sex with anybody who didn't want to have sex with me. But I have, many times, persuaded somebody who didn't find me particularly attractive that they did find me attractive. And I have persuaded them that they wanted to do something, which indeed they did, and they enjoyed.

"But I didn't at the time think: 'How will they react to this in 20 years time, when they're married with children? Will people change as they get older, and might they be badly affected mentally by something they did when they were younger?' I think that's the only regret I have. But you don't think about it when you're young. The hormones are pouring through you, the adrenalin's going, and you just don't think."

A Life in Brief

Born Kenneth George King on 6 December 1944

Education Charterhouse. Studied English at Trinity College, Cambridge

Career Had his first hit with "Everyone's Gone To The Moon" in 1965, many others over the next 15 years. Signed Genesis in 1967 and was involved in the careers of 10cc and The Bay City Rollers. Ran Decca Records before setting up his own label, UK Records. Fronted BBC2's Entertainment USA in the 1980s, and produced the Brit awards from 1990 to 1992. Won British Phonographic Industry's man of the year award in 1997. Convicted of sexual offences involving boys in 2001 and released from prison in 2005. Received an apology from the BBC in October after being cut from a rerun of a 1976 episode of Top of the Pops.