Ever wondered what sleep is? What its role is? What's going on when we're dreaming? What explains sleep-walking? Curious to learn more about pain and its relationship with our bodies? Want to know more about our senses? Dr Guy Leschziner is a consultant neurologist and clinical lead for the Sleep Disorders Centre at Guy's and St Thomas' Hospital in London. Here he shares some his understanding of sleep, pain and how our minds work, and gives his verdict on the crisis in the NHS.