I spend most of my time drawing politicians, trying to work out what makes them distinctive. The eyes, the expression, their mood: it’s all about finding people’s peculiarities and accentuating them. When I started, I’d focus on the face. Everything else was an afterthought. It wasn’t until I came across a drawing by the Norwegian cartoonist Finn Graff – a cartoon of Helmut Kohl, I think – that I realised what I had been missing. How much you can tell from someone’s shoes. I didn’t discover this, so much as rediscover it. When I was a teenager, I worked in a shoe shop in my home town of Arendal, Norway. I used to challenge myself to identify the right shoe for a customer the moment they walked in. It helped that they usually wore some already, of course, because people don’t tend to stray too far from previous choices.