In Cromwell's parliament of 1654, Downing represented Edinburgh, and he represented Carlisle in those of 1656 and 1659. His first diplomatic appointments were to France in 1655 to remonstrate on the massacre of the Protestant Vaudois and as envoy to the Duke of Savoy in 1656. In December 1657, he was appointed resident at The Hague. Although on his earlier years, Downing was strongly anti-monarchical, he was one of the first to urge Cromwell to take the royal title and restore the old constitution.