 The historian Paul Langford has claimed that Harris "proved brilliantly effective as a focus for Orangist and anti-French feeling, and as the agent of Anglo-Prussian cooperation".He returned to England and took an anxious interest in politics, which ended in his seceding from the Whig party with the Duke of Portland in 1793.In that year he was sent by Pitt, but in vain, to try to keep Prussia true to the first coalition against France.