It's an experience we've all had - desperately trying to recall a word. You might know the letter it begins with, the letter it ends with, but it just won't pop into your head. So how will Michael Rosen and Dr Laura Wright cope as we try and induce this most frustrating state: Tip of the Tongue? They are put under the spotlight by psychologist Dr Meredith Shafto, and try to find ways round it with the help of somebody who can memorise a 1000-digit number in an hour - memory Grandmaster Ed Cooke. Producer: Melvin Rickarby.