For one week, six famous faces went back to 1975 to see if living as their more youthful selves could make them physically and mentally younger. In this special, Michael Mosley explores the science behind the series, and tests the idea that we have control over how we age. The programme puts Britain under the microscope to see how our environment, our preconceptions about old people and how we behave ourselves can have enormous impact on how we feel about the elderly and how we ourselves age. A state of the nation programme which shows the remarkable science and extraordinary truths behind the series.