George II and Robert Walpole signed documentA rare 1730 single page document signed by King George II and Robert Walpole, Britains first Prime Minister The document is a warrant to Britains second Prime Minister, Spencer Compton Huge size: 18. 5 x 11 inches Robert Walpole (1676 1745) is widely regarded as Britains first Prime Minister. He held the role, officially the First Lord of the Treasury, for 22 years between 1721 and 1742 making him the longest serving British Prime Minister to date. He