This was taken backstage at the Almeida theatre in 1989, as part of a personal project I was doing on dressing rooms. Tilda [Swinton] was working almost exclusively with Derek Jarman at the time. I remember her saying that, while they were collaborating, she wasn't tempted to do any glamorous or mainstream work; she was interested mainly in the experimental.

I was meant to meet her half an hour before the start of Pushkin's Mozart and Salieri, a two-woman show at the London venue, with Tilda as Mozart. I must have been running late because I ended up having just four minutes with her. I came through the door and discreetly got my camera out. Tilda was only lit by a grubby little bulb, so it's fortunate it came out how it did. She was lost in her thoughts – a lot was going on in her life at the time – so she didn't notice me until I took the first shot.

I think people are regarded as photogenic if pictures capture how they see themselves. A good photograph is open, with neither it nor its subject telling the viewer what to think. This one is all about the subject, but it does have an elegant shape and design, too. When I took up photography at the age of 22, my older brother tried to encourage me by saying my work went beyond a snapshot. Maybe this is an example of what he meant.

CV

Born: 1955, Crowthorne, Berkshire

Studied: Humanities at Bristol, photography at the Polytechnic of Central London and MA at London College of Printing.

Influences: Bill Brandt's black and white portraits; (3), who I spent a bit of time with and who was very helpful.

High point: "Being production photographer for the plays War Horse and Jerusalem."

Low point: "When my entire kit was stolen from my car in 1989. I couldn't afford to replace it."