sentences:  Colsterworth lies one mile to the west of Twyford Wood, which was the site of a Second World War airfield RAF North Witham, and still retains military artefacts, including open runways and a derelict control tower.After the war, the grassed part of the airfield was planted with oaks and conifers.This grassland habitat is home to a regionally important colony of dingy and grizzled skipper butterflies.