Recorded in 2003, it can be found on the How I Draw page of Blake's website.
Blake is now perhaps best known for illustrating Roald Dahl's work. The Dahl books I read as a child, such as Charlie and the Chocolate Factory and James and the Giant Peach, pre-dated the Blake editions and were illustrated by other artists, such as Faith Jaques and Nancy Ekholm Burkert.
However I was still a fan of Blake's work as a result of his wonderful illustrations for the English translations of Nils-Olof Franzén's series of comical crime novels, featuring the Swedish detective Agaton Sax. As you can see, I still have my copies of these marvellous oddball adventures, which are now, sadly, out of print.