Edinburgh - S3.E10

This week Hart-Davis makes the journey to Elgin, re-creating the moment when Alexander Graham Bell invented the telephone, and to the site where James Watt carried out his work on the steam engine.

He also salutes the inventor of the thermos flask, the man who found a way to fight scurvy with citrus fruits, and thesaurus writer Peter Mark Roget, whose work in optics has been neglected.