George Sitwell (1601–67) of Renishaw, in north-east Derbyshire, was involved in the iron trade for most of his life, operating several works in Derbyshire and Nottinghamshire and producing pig and bar iron, wrought ironware, nails and castings. Over 500 outgoing letters throw a mass of light on his activities, especially the trade between the provinces and London. Other letters are concerned with exports, dealings with the Navy Board, money-lending, credit, internal transport and the postal service, as well as public affairs in the capital and Derbyshire, including the Dutch War and the Plague.