30/09/2017 GMT

This month on Witness, Tanya Beckett is back at the British Library in London to introduce us to five people who have experienced important moments of the recent past. We speak to a man who was with anti-apartheid activist and founder of the Black Consciousness Movement, Steve Biko, when he was arrested, a man who was the first to walk the Great Wall of China in its entirety and we hear from a botanist who spent two years sealed inside a giant greenhouse as part of an ambitious ecological experiment.