It's always encouraging when people tell us about something which will enable us to achieve a lot with very little effort. So I was delighted to see a poster on the London Tube the other day launching a new, NHS-sponsored campaign called Think Feet First. The idea is that a very small amount of exercise - that extra flight of stairs, that extra block - can really make a difference to our well-being. So many of us look at 'getting fit' as a torture involving hours at the gym and rigorous diets ...