I was working for Condé Nast and Mademoiselle magazine in New York and had a reportage way of shooting, even for fashion. It caught Andy Warhol's eye; he wanted someone to tag along to parties or to photograph him making silkscreens and movies, capturing his daily life.

For a 24-year-old Englishman, hanging out at the Factory was mind-blowing. I had no idea people lived this way; any time of the day or night, there would be something wild going on. I couldn't afford to get too whacked because I had to stay focused for my work, so I just observed. And a lot of what happened I couldn't photograph: there was no way you could publish those kind of pictures.

On this particular occasion, in the winter of 1964-65, I got a call saying we were to meet at the St Regis hotel: we were going to visit Salvador Dalí, my hero. I was thrilled. When we arrived at his suite, Dalí beckoned us in with a cane and no one spoke; opera music was playing so loudly that the room was vibrating. He grabbed Andy by the arm and plonked him in a chair, pointed at me to get my camera ready, then grabbed a huge Inca headdress, dramatically placing it on Andy's head.

It was pure theatre. Dalí was making Andy so nervous – which was unusual: it was usually him who made other people tongue-tied – that he was guzzling back wine. I'd never even seen him drink before. He kept looking as if he was ready to bolt for the door, and then finally he said: "David, we've gotta go."

There is nothing manufactured about the picture: things happened so fast it was almost like being a war photographer. We were there for no more than five minutes, and we never discussed the experience afterwards. That wasn't Andy's style, and I think he was genuinely shocked by the meeting. Suddenly the table had been turned and it was no longer me photographing Warhol, it was Dalí with Warhol.

Born: Leicester, 1940.

Studied: Leicester College of Art.

Influences: Jacques Lartigue, Cartier-Bresson, Bill Brandt.

Top tip: 'Don't throw anything away. I can't tell you how many times I looked at this huge file of images of Andy Warhol and almost got rid of them.'

High point: 'Awards for my Warhol book.'

Low point: 'Not pressing the shutter when I should have. Shoot the picture and deal with ethics later.'