You often see children depicted in art from the past, less so these days. I like drawing them and notice the particular ways they move and are proportioned. My son Paul, then four, his schoolmate Bibi, six in these images, and a colleague's nine-month-old baby, Dino, were drawn some 30 to 40 times to create animated paintings of moving figures. I have drawn many people walking but Paul was the first running work I made – originally as a proposal for an Olympics project I did not win. I had proposed a whole piazza of different children running on double-sided LED screens.
Dino was then drawn for a giant outdoor project in Calgary, Canada; he would have crawled under a bridge. That project morphed into a 5m-high LED tower, which will go up early next year but without any babies. I am now working on a project for the Lindo Wing at St Mary's Hospital in London. The plan was to use baby Dino in the nursery; this then expanded to include Paul in the corridors, so I needed a girl to accompany him. Bibi and her parents let me film her on my studio walking machine. I picked her because she has nice straight hair that moves in a way that's great to draw.
I often make multiple works such as mugs and fridge magnets. I prefer to make my own rather than leave museum shops to come up with rather random designs. A CD cover can be as good a place for art as a museum wall. When the Guardian asked for a wrapping paper design, I thought children would be the best subject matter. I put the drawings together in a way that was inspired by ancient Greek friezes, pots and traditional wrapping paper. Placed in a row, the repeated figures suggest movement; they could be wrapping around the Parthenon or your Christmas present. If you stare at it long enough, it can also become a magic-eye image.