I walked around the National Portrait Gallery to kill some time. Usually I will draw details from pictures or whole pictures in situ. There's some funny faces in there, that's for sure.

Copying is good practice for drawing. There was a group of kids who were asked to make a drawing of one member of the Capel family in the famous painting. One boy took his piece of paper and walked up to the picture and chose his subject - the Father- then turned around and tiptoed back through the class who were sprawled across the gallery floor in wild postures.

He didn't once look back at the painting for reference as he made his picture. I kept my eye on his progress and by the end of it he stood up and proudly waved the drawing in the air at his teacher. The drawing was definitely no one other than the man in the painting. It didn't resemble the man in the painting at all, but it was the man in the painting.

This is how court artists work. I mean law courts, not Goya. They can't draw in the court but must leave and draw from memory what they saw going on inside. Like smoking, they have to go outside to do it.

I was once asked if I could go to a court case and do some drawings for ABC News. I declined because I was worried my drawing would be too loose and sketchy, and not objective enough, based on what I'd seen of court artist's drawings which are nearly always kind of classically drawn. I think the subjective approach would be more realistic.

Drawing of children drawing at the NPG. Image © David Mackintosh.

Notebook drawing of NPG painting. Photo © David Mackintosh