Johnnie Shand Kydd is showing me a picture of his friend Mr Hirst -- naked with a cigarette attached to his penis.

"Damien is very generous," he says, "for the want of a better word, with his body, I suppose." Asked how did he got him to pose like that, Johnnie stifles a laugh.

"You really don't have to try hard. There was a period when he wouldn't put it away."

We are leafing through a book of Johnnie's photographs in the new Sebastian Guinness Gallery on Dawson Street in Dublin. (He has a photographic exhibition on Naples running with the late John Deakin's images of Genoa.) He points out images of a young and dishevelled-looking Tracey Emin at a party in Margate, a character called Big Sue who Lucien Freud painted; and one or two people who are no longer with us.

"That's the awful thing about chronicling a generation, people just fall off the merry-go-round," Johnnie says.

He fell off his bicycle eight years ago. He put the subsequent photograph of himself after the accident on the cover of the book with a bandaged, scarred face. Johnnie Shand Kydd's career -- although Johnnie would doubtless hate the word "career" -- is a bit of an accident too. Born on May 2, 1959, in London, he didn't even started taking photographs until he was 35. He decided he couldn't stand the job he was in "another second longer".

Prior to that cultural epiphany of sorts, Johnnie had worked in a Bond Street art gallery selling 19th Century paintings for 15 years.

"I just walked out one day having no idea what I was going to do next," he explains. "Then I realised I knew a lot of people who were young artists. I just had a sense that something was about to happen. I didn't know how to take a photograph. But I thought better to have a good story and no talent than to have no story and no talent," he laughs.

Where did the desire for the story come from?

"Friends of mine say I was a photographer before I took up a camera," he replies. "I suppose I'm an observer and a storyteller."

I ask to what extent he inherited that from his parents. He says that his father's background was in the family wallpaper factory -- "so design was something that was integral to him I suppose, to his upbringing -- and my mother has always been involved in the art-world. So, I always knew artists."

Johnnie's upbringing wasn't the most conventional. His late father Peter Shand Kydd was a farmer before inheriting the family business. He sold off the company when Johnnie was three and brought his wife Janet Munro Kerr and family to a farm in Australia.

"It was a fantastically liberating place," he remembers. "It was out in the outback really. As a five year old, I would go out with a pony and the pony would come back three hours later and an hour later I would come back crying. Nobody thought to come to look for me. I think that independence as a child is a fantastic thing. But you wouldn't be allowed to get away with it in this day and age."

This notion of independence is how his Naples project happened. "I just like disappearing and going off places in the world," he says.

The Shand Kydds returned when Johnnie was seven or eight -- roughly around the time his father bolted with Princess Diana's mother to the west coast of Scotland leaving Johnnie's mother with him, his older siblings Adam and Angela in East Anglia. (In May 2004, novelist Adam, who was 49, died of an apparent overdose in Cambodia.) "My parents were divorced," he recalls. "We all got on very well together, all over the place. I think my mother probably had custody."

So were you shuffling between both of them in the west coast of Scotland and East Anglia?

"Yes, but I was also sent off to boarding school," he says of his hideous time at English public school Rugby.

"It was a completely bizarre place." And how: he once recalled that "at my prep school you were given a choice between weapons -- you could either be beaten with the hardbacked hairbrush or the slipper. Imagine thinking, 'Which pain shall I choose today?"'

"I had such a profound loathing of authority," Johnnie, who was sent to boarding school at seven, recalls. "Anyone in a uniform even now -- anyone -- who tells me what to do rises every hackle and I hate it. I think I got the tail-end of that type of education whereby those English public schools were trying to create the last people who you could send out to run empires in a way; you were encouraged not to ask questions, to obey orders. It was trying to make you into a robot and I just fought it tooth and nail. So, I think it is quite healthy to have a hatred of establishment."

Johnnie Shand Kydd's famous stepsister had a similar hatred of establishment, of course, too...

I'm told by someone who knows Johnnie that the subject of Lady Diana will have be approached creatively if at all. So I tell him how his steppie, in March 1997, dropped by Cork aristo photographer Bob Carlos Clarke's studio in London with a mutual friend. Her eye was drawn to an erotic image of a woman's peachy derriere framed on the wall. "I recognise her

bum," Princess Di told Bob. "I went to school with her."

Johnnie smiles at the story.

"She was much brighter than people give her credit," he says. "She inhabited a world where image is so much to do with artifice, and she was very good at it, and she worked with photographers who were very good at it too. But I don't think it ever sort of ... " He stops himself.

"But I don't know whether photography is ever a medium really which is about getting to the essence of somebody's soul. It tends towards the surface."

I chance my arm with another question. What was she like?

"I can't paraphrase it. She was a complicated character, as we all are. I wouldn't even know how to begin. I would feel terribly uncomfortable. I know it is the question that everybody wants to ask."

After our interview, Johnnie is going to stay at Sebastian's place down the country with Sebastian and his wife before flying back to London. He is tall and skinny and witty and grandly-spoken (he doesn't always say nice things but he says it in a slightly grand accent.)

It all began when he started taking photographs of his artist friends -- the Young British Artists aka YBAs -- such as Tracey Emin, Sam Taylor-Wood, Sarah Lucas and the aforementioned Damien Hirst years before they became household names.

"They were all bouncing ideas off each other. The bar became an extension of the studio. Once you met one, you met them all. That world is basically gone now. They have all gone their own directions. They don't need each other any more or they don't like each other any more. But I haven't fallen out with that lot," he laughs.

Lynn Barber once described him thus: "For years he just seemed to be the posh poof -- Princess Diana's stepbrother -- at the court of the YBAs, who hung out with Damien and Sam and Sarah and Tracey, and occasionally produced an Instamatic camera and took a snap.

"When those 'snaps' emerged in the 1997 book Spit Fire, Charles Saatchi got him to take all the portraits for the Sensation catalogue; Johnnie Shand Kydd's star was officially and firmly rising in the firmament."

I say to Johnnie Shand Kydd that I know nothing about him other than his photography.

"I'm gay. I'm somebody who is passionate about my work and I'm passionate about friendships. I'm in a relationship for four years."

He lives in London but he says he is always travelling.

"I was thinking about this earlier: I think if I'm feeling too socially comfortable and I know how my life is going to map out too much then it deadens your senses. So I find the best work I do is going somewhere where I feel slightly displaced and a little bit uncomfortable and the rug is pulled from under my feet a bit."

What would Freud say about that? Why do you feel more comfortable being uncomfortable?

"I have no idea. It makes my work better. I am very comfortable with my own company. And I think if you get on with yourself you tend to get on with other people."

For the Naples project, he says, you can go to another country just laden down with prejudices "and I think you owe it to other cultures, especially if you pretend to love the place, to give it a lot of time and thought and hopefully chip away until you find the kernel of what the truth is".

And if I was to chip away to find the kernel of truth in Johnnie Shand Kydd?

"Something very dark in the bottom of the wood shed," he laughs. "I don't think I particularly like happy-happy sort of people. Happy-clappers. You have to get a happy balance. There is nothing worse than somebody who is absolutely depressive too," he adds. "I think you have to have peaks and troughs in your life."

And where are you now?

"I'm terribly good."

Are you in love?

"Oh, yes!"

A Tale of Two Cities: John Deakin -- Genoa and Johnnie Shand Kydd -- Naples runs until December 10 at The Sebastian Guinness Gallery, 42 Dawson Street, Dublin 2. Tuesday to Friday 10-6pm, Saturday 12-6pm. www.sebastianguinness gallery.com

- Barry Egan