Snapshot of Brighton passer-by scoops prize

Joe Mocham was meandering along Brighton's seafront when he was asked to pose for a picture by a stranger. Suspicious at first, he came round to the idea after the man explained that he was a photographer putting together portraits for a competition and he only wanted a "very informal, quicky shot".

The encounter was over in less than five minutes and Mr Mocham thought nothing more of it. That is, until yesterday, when the photographer in question, Richard Boll, scooped the National Portrait Gallery's prestigious £12,000 prize for the striking portrait, "Joe".

Mr Boll, 29, last night explained that he had taken the picture as part of a larger project on strangers on the streets of Brighton, and the final product demonstrated "spontaneous interaction" between passers-by.

The prize-winning photograph was taken outside his flat and was of the first of 50 strangers he stopped over three months.

"I asked Joe outside my flat and he was welcoming. I spent about three or four minutes with him. I'm wary about keeping people too long. It's not about their lives or where they come from or what they do. He just looked visually interesting.

"Joe insisted he wasn't photogenic. I disagreed. With this kind of portraiture, there's a level of trust that has to be won in a short space of time, and I always tell my subjects to be themselves. It lets them know I'm not out to misrepresent them.

"I lost touch with Joe but when I was shortlisted, I went looking for him with his picture, asking people in pubs 'have you seen this man?' I finally saw him outside a café and he was really pleased," he said.

Mr Mocham, 37, who has previously been homeless and is living in a hostel in Brighton, was delighted by the idea that his portrait now hangs in the gallery.

"I thought it was weird at the time when he asked me. I usually walk around looking a bit glum. God knows why he was drawn to me, and I asked him if he was doing a college course. I am so proud that it's in the National Portrait Gallery and I will go and see it," he said.

Mr Boll explained how the 20 selected portraits in the series, Pavement, represented a move away from conventional portraiture where the artist was well acquainted with subjects.

"It can be anything that draws me to a stranger, a splash of colour on clothing, a certain look, I tried not to go out with an agenda and I wanted to leave it as open as possible. There is something nice about a quick encounter. When you photograph someone you know well, there is a lot of baggage.

"When you meet a stranger, it's fresher, and you get an effective picture of them rather than getting a portrait in a more conventional sense," he said.

He said he was heartened by how well-received he was.

"I took pictures of a spectrum of people, men, women, couples, people with their dogs. Part of my intention for this series was enjoying being in Brighton which is so liberal-minded and open. I felt I got a good response and that I wouldn't have got the same response in other places where people are more closed," he said.

Born in Kenya but brought up on the Isle of Wight, Mr Boll began taking photographs as a teenager and graduated from Edinburgh College of Art in 1999. He had been shortlisted with three others, who were picked from more than 2,000 entrants in the fourth year of the international award. Anna Bauer received the £1,500 second prize while Kiran Master was awarded third prize for and Kyoko Hamada came in fourth place.

Sandy Nairne, director, National Portrait Gallery, said the winners demonstrated "the vitality of photographic portraiture today".

Their work will be shown alongside another 50 of the submitted portraits.