Dr Guy Meadows is a specialist in chronic insomnia and clinical director of The Sleep School, London Dr Guy Meadows is a specialist in chronic insomnia and clinical director of The Sleep School, London Derk-Jan Dijk is professor of sleep and physiology at Surrey's Sleep Research Centre Gillian Twigg is principal clinical scientist at the sleep centre at Imperial College Healthcare NHS Trust Dr Guy Leschziner is a consultant neurologist at the sleep disorder centre, Guy's and St Thomas' hospitals, London Guy Meadows A lot of the symptoms associated with a hangover are a product of sleep deprivation.