In common with many other Jacobites, Williams-Wynn's support was conditional on a substantial French military landing in England. When Charles Stuart invaded England during the 1745 Rising, Williams-Wynn remained in London to attend Parliament, only sending an oral message promising help when a French army arrived, an offer that arrived too late to help Charles. After the Rebellion ended, the testimony of Prince Charles' former secretary Murray of Broughton led to the execution of Lord Lovat; he also implicated a number of Tories, including Williams-Wynn and Cotton but the government decided against further prosecutions.