This article lists each Prime Minister of the United Kingdom in order of term length. This is based on the difference between dates; if counted by number of calendar days all the figures would be one greater. Of the 55 Prime Ministers, nine served more than 10 years while seven have served less than a year. Robert Walpole is the only person to have served as Prime Minister for more than two decades. George Canning served for less than four months before his death.