 He and Sir Francis Bassett of Tehidy were given the responsibility for levies from the West of Cornwall for the Second Bishops' War.After the Treaty of Ripon he hurried back to stand for Parliament.In October 1640 Slanning was elected for both Plympton Erle and Penryn to the Long Parliament (in a way which was to give rise to charges of bribery), and chose to sit for Penryn.