 He then acquired Featherstone Castle near Haltwhistle, Northumberland and remodelled it in the 1830s to a Gothic style.Wallace was a Member of Parliament (MP) for Grampound from 1790 to 1796, for Penryn from 1796 to 1802, for Hindon from 1802 to 1807, for Shaftesbury from 1807 to 1812, for Weymouth from 1812 to 1813, for Cockermouth from 1813 to 1818 and again for Weymouth from 1818 to 1828.He was Lord of the Admiralty from 1797 to 1800.