In 1639, both father and son fought in the Bishops' Wars against the Scots. They later fought for the Royalist side in the First English Civil War. In 1643, the two led a failed conspiracy whose purpose was place the town of King's Lynn under Royalist control. Roger L'Estrange's subsequent activities as a Royalist conspirator lead to him spending time in prison under sentence of death. He later played a leading role in the 1648 Royalist uprising in Kent. This was defeated by parliamentarian troops and he fled to the Continent, finding refuge in Holland.