I had a ticket on Monday to another of these "Insight evenings" - public open classes at the Royal Ballet - and just as I got into central London I realised I'd left my sketchbook at home.
I dashed into a stationers and bought their cheapest A6 sketchbook, which turned out to have brown paper pages. I thought I'd wasted my £3 - but it turned out to be a pleasure to draw on. It took my 4B pencil really smoothly and without smudging, and gave a lovely rich soft line. I filled nearly a third of the pages at the one sitting.