Dr Paul Kelley said that adolescents effectively lose up to two hours of sleep per day, which is “a huge society issue”.

He and colleagues from Oxford are leading a project called Teensleep, which is currently recruiting 100 schools from around the UK to take part in what Dr Kelley called “the world’s largest randomised control trial”, due to commence in 2016.

Our body clock is a daily cycle which drives the regular rise and fall of certain genes as well as the ebb and flow of our cognitive performance, our metabolism and so on.

For much of our lives – and especially in adolescence – there is a mismatch between this rhythm and the typical working day.