The English artist takes us into his whimsical trompe d'oeil three-dimensional sidewalk chalk drawings in The Pavement Chalk Artist.

As a person who can't draw at all, anamorphic drawing looks much more difficult. Is it?

A nonanamorphic drawing is one that is designed to be looked at face-on. An anamorphic drawing is different: we don't view it face on and we are not supposed to. We view it from a particular angle and from one viewpoint only. It is drawn in a stretched form so that from that single viewpoint, these forms, compressed from the effects of perspective, appear correct. This being the case, we can make objects appear to be either standing on the pavement or going into the pavement. You can make things look 3D. They are more challenging to draw because you have to draw all the forms in a distortion so that they look right from your viewpoint.

"Swimming Pool in the High Street" was your starting point with anamorphic pavement drawing. What were you doing before?

I was drawing conventional pavement pictures—portraits of the famous, copies of old masters. There was one particular street in Brussels that had large rectangles of tiles set in the pavement, relics of some small gardens that had once existed. I used these rectangles of tiles as frames for my drawings as they were just about the right size and there was a lovely textured surface within them. I had done this many times when one day I suddenly realized I could use these tiles as if they were the outside surround of a mini-swimming pool. All I had to do was color them and then fill in the pool inside. Half the work had already been done! I was so impressed with the result and it was such a change from the rut I'd got into, that I had to do more.

As a street artist, have you had run-ins with law enforcement?

I have had many run-ins with the law, although none of these have ever really got ugly. It normally happens when you are trying out a new place without any sort of authorization. Sometimes you get away with it, sometimes you don't. Once outside Liverpool Street station in London they called in a cleaner and washed off my work in front of me. But that was an exception. Often you can negotiate. My policy used to be to comply absolutely, thank them for stopping me, shake their hand, and leave quietly. Then I'd come back in an hour and start again.

Of all the pieces in the book, "Down the Drain" is the most explicitly political. Is this the beginning of a trend? Do you see yourself offering more social commentary in your work in the future?

I don't think so. If I had to summarize what my work is about, I would say the wonder of things. The drawing you mention was done the week before the [last] U.K. election and it seemed a good time to stick my oar in. The previous "political" one was for the 1997 election. So once every 13 years seems about right to me.

You've done these drawings all over the world. Is there any pressure to outdo yourself with each piece?

The pressure is from within. It's always a wonderful feeling to do a good picture or something different from what has gone before. I don't have any idea what will be next, but then again, I never did.