Who's your favourite Sherlock Holmes? Benedict Cumberbatch or Rob Downey Jr.? Jonny Lee Miller or Jeremy Brett? It's so hard to choose, so spare a thought for poor Dr Watson - faced with so many Sherlocks old and new, what will he do? Who's so the wrong height? Who's too black and white? Who's too pale of face? Who's in the wrong place? Who's the right Sherlock in Doc Watson's view? And is Watson's Sherlock the Sherlock for you?

Who's your favourite Dr Watson? Martin Freeman or Jude Law? Lucy Liu or Edward Hardwicke? It's so hard to choose, so spare a thought for poor Sherlock Holmes - faced with so many Watsons old and new, what will he do? Who's too techno-garish? Who's too teddy-bearish? Who's maybe too pretty? Who's in the wrong city? Who's the right Watson in Holmes's own view? And is Sherlock's Watson the Watson for you?

This book of photocopiable puzzles, that may be used in the classroom and at home, is the result of a request from the World Memory Sports Council (WMSC), the governing body for the World Memory Championships (WMC), to create an international memory competition for pre-schoolers. I decided from the outset that it needed to be fun, stress-free and independent of language: not only for the young pre-reading age children but also for the parent/teacher guiding them.

Visual memory training is nothing new. The Ancient Greeks valued it highly but until recently it seems to have been seen...