We all have a biological clock ticking away inside us that governs our daily rhythms. This affects our health as much as our diet and whether we exercise. So what can we do to manage this internal clock better? To find out, evolutionary biologist Ella Al-Shamahi locks former commando Aldo Kane in an abandoned nuclear bunker with no way of telling the time - for ten days. Monitored around the clock by a team of scientists, he carries out a barrage of tests to uncover exactly what makes our body clock tick. Above ground, Ella meets two time-starved couples to test the latest thinking on how we can manage our body clocks better. In trying to improve their sleep, and their lives, she uncovers practical advice that we can all take on board. Studies on shift workers show that regularly disrupting our sleep makes us more at risk of diabetes, heart disease and even cancer. So getting to grips with our biological clock couldn't be more important.