<page_title> List of Prime Ministers of the United Kingdom by age </page_title> <section_title> List of prime ministers </section_title> <table> <cell> Duke of Grafton <col_header> Prime Minister </col_header> </cell> <cell> 41 years, 45 days <col_header> Length of retirement </col_header> </cell> </table>
Grafton had the longest post-premiership of any prime minister in British history, totalling 41 years and 45 days.