He took no part in the 1648 Second English Civil War, even though his younger brother Charles Lucas (1613–1648) led the Royalist defence of Colchester and was executed after it surrendered.

[2] The youngest was Margaret (1623–1673), a prolific author and scientist who in 1645 married William Cavendish, 1st Duke of Newcastle (1593–1676), formerly Royalist commander in Northern England during the First English Civil War.

As part of a policy of securing the allegiance of professional soldiers like Lucas, in December 1638, the Chief governor of Ireland, Thomas Wentworth, 1st Earl of Strafford, suggested giving him a position in the Irish Army.

[7] As Royalists in a county dominated by supporters of Parliament, the Essex-based Lucas family was of greater significance than it might appear and at the same time his brother John joined the newly-established household of the eight year old Prince of Wales.

Lucas took part in operations to recover territory lost to the rebels, including the Battle of Kilrush on 15 April 1642, before the outbreak of the First English Civil War in August ended the flow of reinforcements and money from England.

Although his younger brother Charles was executed after the Siege of Colchester, Lucas himself did not participate in the 1648 Second English Civil War and died at home in Lexden before October 1649.