Walking upright on two feet is a uniquely human skill. It defines us as a species. It enabled us to walk out of Africa and to spread as far as Alaska and Australia.

It freed our hands and freed our minds. We put one foot in front of the other without thinking - yet how many of us know how we do that, or appreciate the advantages it gives us?

'Will leave you itching to go out for a good old-fashioned stroll' Mail on Sunday

'Informative and persuasive enough to rouse the most ardent couch pototo' New Scientist