You can tell he's not a victim. Robert is a survivor, who delivers his polemic with a familiar passion. The tall teenager with the floppy black fringe slouches back in his chair like a certain chippy pundit on late- night television. His words have the rhythm of a writer who shoots from ample hips. Truly, this is the son of Big Mouth and the Queen of the Groucho: Tony and Julie, Parsons and Burchill, the NME lovebirds who became true enemies; the husband and wife who chose to slog out the pain of their parting in public.
Their 15-year feud remains entertaining because of the skill with which the two professional polecats pursue it, even while feigning weariness. Their son has always kept clear of all that nonsense, and never allowed himself to be interviewed before.
But Bob, as his friends call him, is a 19-year-old man who loves his dad dearly. Wants to be like him, even. So he has agreed to talk, in a Brighton coffee shop, to help promote the old fella's novel, Man And Boy, which is about a father who brings up his son alone when the mother walks out.
"There's no Julie in it," Parsons said before allowing me to meet his son. "None at all. That whole Tony and Julie thing bores me to tears."
And yet the similarities make comparisons inevitable. Pat, the boy abandoned in the book, is a five-year-old obsessed with Star Wars, who turns to his grandparents for comfort only to lose one of them to cancer. All of which was roughly true of Bob when his mum left the family home in Billericay. He didn't see her again for more than a decade.
Far from attacking by proxy, Tony has advised his son not to say anything about Julie. But the child of our two most outspoken commentators has inherited their frankness. Even before the cappuccino has gone cold he admits to not having liked any of his father's partners before Yuriko, the present Mrs Parsons. What was wrong with them?
"One you're aware of. The rest were a bit too much like her."
In what way? "I always felt more like an inconvenience than an added bonus. On the parenting side of things, it has always been about me and Dad."
They had their hard times. At 14, Bob was confined to bed by a thyroid illness that kept him off school for more than a year. When he got better he got angry at the whole world, and rebelled as his father had. There was no point in the old man reminiscing about the emptiness of casual sex and taking drugs with the Sex Pistols, Bob had to take his own chances. "I walked down to the crossroads of screwing up my whole life, and decided to get the bus back at the last minute," he says. "I can see it would have been hard for Dad."
His anger now is at the injustices of the world, which he would love to confront as a journalist, just like the father he so admires. And like his mother, although she hardly inspires the same affection. Bob does not remember her original departure, but has vivid memories of how she came back into his life. "That was the whole reason I moved down here."
Head down, he clinks the spoon around his cup. It has not worked out too well, life in Brighton.
We're supposed to be talking about men and boys, but first he wants say something about that woman. They do not get on. "We did briefly, but I think the novelty of me wore off."
The mother and child reunion happened just over two years ago, after Julie Burchill and her son met by accident in London. "She was very apologetic. She got tearful, and it was a whole melodramatic soap-opera type thing. Then I got a letter and she was, `Come down and live with me.'
"So I did, just after my 17th birthday, and before I knew it, she was like, `Right, I'm so glad to have you living here, but you can't be here on weekends'. I wasn't welcome. Could I leave between Friday and Monday turned into between Friday and Thursday. I was spending five nights a week at my mate's house in London."
The end came when he was in Islington house-sitting for his father. "I got a letter that she must have posted to my dad's address as soon as I'd left the last time, which said, `I want you to move out'."
Bob last saw his mother a year ago. "I didn't speak to her for quite a while, and then she had one of her tearful little scenes when I went to pick up some stuff. She lives 10 minutes down the road from me but she thinks that I live a bit further away."
Bob does not regret the move entirely. The slight deformity of his right arm, which he self-consciously refers to often as "my disability", has not stopped him playing football at a semi-professional level in Brighton. He is half-way through A-levels, and has learned a lot about himself.
"I just wanted to get to know my mum. No matter what you hear about people, you like to know for yourself. It was a demon I'd carried around with me for God knows how long, that needed exorcising."
So the demon has been exorcised now? "Definitely."
Father and son, on the other hand, are very close and see each other at least once a week. Man And Boy is a work of fiction - a perceptive and funny one at that - written from experience. As a freelance writer, Tony Parsons was able to take his young child to the park in the mornings just as Harry, the unemployed television producer in the book can do. But even as he described those days to me, Tony got bashful. "Actually, it has been overstated. The reality is that my son and I spent one year living together in a flat on our own, but the following summer my girlfriend moved in. I've been passed from woman to woman, from my mum onwards."
Emma Parsons, mother and nan to the Parsons boys, died two months ago. "I spent so much time there, she was a mum and a grandmother to me," says Bob. "I miss her a lot. I'm still adjusting to it now. I'm at a loss about what to do."
He will spend the summer back at her house in Billericay, which he considers home. "I would go up the shops, cook for her and everything, but when we watched TV in the evenings I would have to sit close and watch her suffer, knowing there was nothing I could do. For the first time now I can sit in that house and think about the good times instead."
Tony Parsons loved the way his son cared. "For the last year he spent pretty much every weekend with her. I really admire him in a way that I admire my dad."
A considerable tribute, that. Tony Parsons needs little prompting to talk about the strength and gentleness of his father, a wartime commando who became a greengrocer. He died from cancer, 12 years ago, like the grandfather in Man And Boy. Before getting ill, the fictional version is able to overpower two young burglars and tie them up. "A Freudian would say that cut to the heart of the way I felt about my father as the Great Protector, and my inability to measure up to him because I could never do a thing like that in a thousand years," Tony told me. Would the psychiatrist be right? "God, yeah."
On television and in print he has long argued that the children of today are paying the price for their parents' sexual liberation. "Growing up in a strong family background made me feel I could do anything if I worked hard enough and got the lucky breaks. When the world was kicking me about, that was where I could go and lick my wounds."
Not surprisingly, Bob also covets the old certainties. "I'll marry once. I can't fault my dad - they split up, and that's the way things go - but at the end of the day I didn't have what he had, the security. Some days it doesn't matter. Some days you're really aware of it - the thought that the two people who should be closest to you would always be there. I've never had that."
`Man And Boy' is published by HarperCollins, pounds 12.99.Reuse content