List of British Prime Ministers since the post began

Eighteenth Century

1721 to 1742: Sir Robert Walpole (Whig)
1742: Spencer Compton, Earl of Wilmington (Whig)
1743 to 1754: Henry Pelham (Whig)
1754 to 1756: Thomas Pelham-Holles, Duke of Newcastle (Whig)
1756 to 1760: William Cavendish, Duke of Devonshire (Whig)
1760 to 1762: Thomas Pelham-Holles, Duke of Newcastle (Whig)
1762: John Stuart, Earl of Bute (Tory)
1763 to 1765: George Grenville (Whig)
1765: Charles Watson-Wentworth, Marquess of Rockingham (Whig)
1766 to 1768: William Pitt the Elder, Earl of Chatham (Whig)
1768 to 1770: Augustus Fitzroy, Duke of Grafton (Whig)
1770 to 1782: Frederick North, Lord North (Tory)
1782: William FitzMaurice, Earl of Shelburne (Whig) Charles Watson-Wentworth, Marquess of Rockingham (Whig)
1783: William Bentinck, Duke of Portland (Tory). William Pitt, the Younger (Tory)

Nineteenth Century

1801 to 1802: Henry Addington (Tory)
1804 to 1806: William Pitt, the Younger (Tory)
1806: William Grenville, Lord Grenville (Whig)
1807 to 1809: William Bentinck, Duke of Portland (Tory)
1809 to 1812: Spencer Perceval (Tory)
1812: Robert Jenkinson, Earl of Liverpool (Tory)
1813 to 1827: Robert Jenkinson, Earl of Liverpool (Tory)
1827: Frederick Robinson, Viscount Goderich (Tory) 
George Canning (Tory)
1828 to 1830: Arthur Wellesley, Duke of Wellington (Tory)
1830 to 1834: Charles Grey, Earl Grey (Whig)
1834: Sir Robert Peel (Tory) 
Arthur Wellesley, Duke of Wellington (Tory)
1835 to 1841: William Lamb, Viscount Melbourne (Whig)
1841 to 1846: Sir Robert Peel (Tory)
1846 to 1852: Lord John Russell (Whig)
1852 to 1855: Edward Stanley, Earl of Derby (Conservative Party)
 George Hamilton-Gordon, Earl of Aberdeen (Conservative Party)
1855 to 1858: Viscount Palmerston (Liberal Party)
1858 to 1865: Viscount Palmerston (Liberal Party) 
Edward Stanley, Earl of Derby (Conservative Party)
1865: John Russell, Earl Russell (Liberal Party)
1866 to 1868: Edward Stanley, Earl of Derby (Conservative Party)
1868 to 1874: Benjamin Disraeli (Conservative Party)
 William Ewart Gladstone (Liberal Party)
1874 to 1880: Benjamin Disraeli (Conservative Party)
1880 to 1885: William Ewart Gladstone (Liberal Party)
1885 to 1886: Marquess of Salisbury (Conservative Party)
1886 to 1892: William Ewart Gladstone (Liberal Party)
 Marquess of Salisbury (Conservative Party)
1892 to 1894: William Ewart Gladstone (Liberal Party)
1894: Earl of Rosebery (Liberal Party)
1895 to 1902: Marquess of Salisbury (Conservative Party)

Twentieth Century

1902 to 1905: Arthur Balfour (Conservative Party)
1905 to 1908: Henry Campbell-Bannerman (Liberal Party)
1908 to 1916: Herbert H. Asquith (Liberal Party Coalition Government)
1916 to 1922: David Lloyd George (Liberal Party Coalition Government)
1922: Andrew Bonar Law (Conservative Party)
1923 to 1929: Stanley Baldwin (Conservative Party)
1929 to 1935: James Ramsay MacDonald (Labour Party)
1935 to 1937: Stanley Baldwin (Conservative Party National Government)
1937 to 1940: Neville Chamberlain (Conservative Party National Government)
1940 to 1945: Winston Churchill (Conservative Coalition Government)
1945 to 1951: Clement Attlee (Labour Party)
1951 to 1955: Winston Churchill (Conservative Party)
1955 to 1957: Sir Anthony Eden (Conservative Party)
1957 to 1963: Harold Macmillan (Conservative Party)
1963: Sir Alec Douglas-Home (Conservative Party)
1964 to 1970: Harold Wilson (Labour Party)
1970 to 1974: Edward Heath (Conservative Party)
1974 to 1976: Harold Wilson (Labour Party)
1976 to 1979: James Callaghan (Labour Party)
1979 to 1990: Margaret Thatcher (Conservative Party)
1990 to 1997: John Major (Conservative Party)
1997 to 2007: Tony Blair (Labour Party)

Twenty-First Century

2007 to 2010: Gordon Brown (Labour Party)
2010 to 2015: David Cameron (Conservative/Liberal Coalition)
2015 to 2016: David Cameron (Conservative Party)
2016 to 2019: Theresa May (Conservative Party)
2019: Boris Johnson (Conservative Party)