Tea is still the UK's favourite drink - but what's the human cost of a cuppa? In the first of a new series of File on 4, Jane Deith reports from Assam on the plight of workers on tea plantations which help supply some of Britain's best known brands. India is one of the largest tea producers in the world with an industry worth billions of pounds - but critics say pickers often have to endure long working hours and insanitary conditions, leading to poor health and high levels of maternal and infant mortality. Producer: Sally Chesworth.