Whilst sketching at a picnic, the shadows of grass blades crept over my sketchbook and bid me to attend to them rather than the scene in front of me.

Recording them was rewarding - I drew them in a sequence, and as I did so realise how the pressure of my pencil on the paper shifted and changed the shadow. Once each blade had been drawn, I started over, this time with a different colour, showing the movement of the shadows against the time taken to draw them.

But when removed from the shadows, the image lost its compelling quality for me. It was lucky my friend had a camera which I could use to record it in situ.