Halley is the UK's most isolated station (75.35S, 26.39W) and is afloat on an ice shelf on the mainland of Antarctica. In winter there is darkness for 105 days - darkness relieved by magnificent auroral displays. The relief of Halley is a major undertaking with supplies being landed twice a year by ship onto the ice shelf and then towed on sledges by Sno-cats to Halley, some 12 km distant from the ice edge.