 On the outbreak of the First English Civil War Legge joined the king's army, and was taken prisoner in a skirmish at Southam, Warwickshire, on 23 August 1642.Committed by the House of Commons to the Gatehouse Prison he escaped about 4 October 1642, and rejoined Charles at Oxford.Henceforth he closely attached himself to Prince Rupert, and was wounded and again taken prisoner while under his command at the siege of Lichfield in April 1643.