Like many people who pride themselves on having a good memory, Elaine Frank got a shock when she forgot where she’d parked her car during a trip to the supermarket. “It felt like a wake-up call,” says the 54-year-old bookkeeper from East Sussex. “The thought of my memory failing has always been a worry and this seemed to be a sign that it was starting to deteriorate.”

Since then, Frank has spent part of every day on a mental work-out, memorising her clients’ VAT numbers – and the fact that each day it is becoming increasingly easy to do has convinced her that it is making a difference.