English county on the eastern side of the Irish Sea and the principal mainland base of the Stanley Lords of Man.

The Stanleys held extensive estates in Lancashire, particularly around Lathom and Knowsley, while governing the Isle of Man for much of the fifteenth, sixteenth and seventeenth centuries. Their position linked Manx government directly with the politics of north-west England.

That connection became especially important during the Civil Wars. James Stanley, seventh Earl of Derby, raised forces in Lancashire for Charles I while retaining control of Mann. Parliamentary authorities repeatedly feared that the Island might be used to support Royalist activity on the mainland. During the conspiracies of 1651 vessels were sent towards Mann to prevent troops landing from the Island in Lancashire, and General Blake was appointed to command a squadron watching the Irish Sea.

Derby returned from Mann in 1651 to join Charles II. His hastily raised Lancashire force was defeated by Colonel Robert Lilburne at Wigan on 25 August. Wounded, Derby escaped and continued to Worcester, where he joined the king before the final Royalist defeat.

After Worcester he was captured, tried under the Commonwealth Act prohibiting correspondence with Charles Stuart, and condemned to death. The sentence ordered that he should be beheaded at the market place in Bolton.