I saw a show about him on TVO about a year ago. They brought him into a helicopter and flew over London for about 15 minutes, and over the course of a week he drew a 10 foot wide panorama of the City, from memory, with details right down to individual rowhouses. You can watch the video of it here
. (London Panorama, top right.) Aside from his amazing drawing, there are lots of cool aerial shots of the city.