After Cromwell's death Herbert then joined the party that demanded a "full and free parliament", in practical terms demanding the Restoration of the House of Stuart. He was involved in the royalist plot of July 1659, and was committed to the Tower of London, whence he wrote to his wife on 20 August 1659 a letter taking a justly sanguine view of his situation. He was released on 1 November 1659, and was elected MP for Monmouthshire and for Wootton Basset in 1660; he chose to sit for Monmouthshire in the Convention Parliament. In 1661 he was re-elected MP for Monmouthshire in the Cavalier Parliament and sat until 1667 when he inherited a peerage.