British prime ministerial statistics

Now that Theresa May is set to become Prime Minister on Wednesday, it's worth noting that it's rather rare for a Home Secretary to become PM. That's not a coincidence: as minister for such matters as the police and immigration, it's full of political traps and is consequently rarely sought after by the politically ambitious, who fear it'll be the graveyard of their reputations rather than the making of it. (See Jacqui Smith, Gordon Brown's first Home Secretary, for a typical trajectory.)

Yet May, who was probably not thinking of ever moving up when she took the job, has managed neatly to avoid most of this. And not only is she merely the fourth Home Secretary to become PM since back in the mid-19th century, she is also the only Home Secretary who had not also held one of the other top jobs (Chancellor of the Exchequer or Foreign Secretary) to become PM in all that time too.

Just to wig you out further, here's a list of all the PMs since the First Reform Act (by their first date in that office) with their previous Cabinet experience.

Lord Melbourne (1834): Home Secretary (3 yrs, 8 mo.)
Sir Robert Peel (1834): Home Secretary (8 yrs, 1 mo.)
Lord John Russell (1846): Paymaster-General, Home Secretary, War and Colonies (9 yrs, 9 mo.)
Lord Derby (1852): Chief Secretary of Ireland, War and Colonies (8 yrs, 2 mo.)
Lord Aberdeen (1852): Chancellor of the Duchy, War and Colonies, Foreign Secretary (8 yrs)
Lord Palmerston (1855): Secretary at War, Foreign Secretary, Home Secretary (21 yrs, 8 mo. - all-time tops in previous experience)
Benjamin Disraeli (1868): Chancellor of the Exchequer (3 yrs, 9 mo.)
William Gladstone (1868): President of the Board of Trade, War and Colonies, Chancellor of the Exchequer (9 yr, 7 mo.)
Lord Salisbury (1885): India Secretary, Foreign Secretary (6 yrs, 10 mo.)
Lord Rosebery (1894): Commissioner for Works, Lord Privy Seal, Foreign Secretary (2 yr, 4 mo.)
Arthur Balfour (1902): Secretary for Scotland, Chief Secretary for Ireland, 1st Lord of the Treasury (13 yrs, 9 mo)
Henry Campbell-Bannerman (1905): War Secretary (3 yrs, 3 mo.)
H.H. Asquith (1908): Home Secretary, Chancellor of the Exchequer (5 yrs, 3 mo)
David Lloyd George (1916): President of the Board of Trade, Chancellor of the Exchequer, Minister for Munitions, War Secretary (11 yrs - all continuously, without a break)
Bonar Law (1922): Colonial Secretary, Chancellor of the Exchequer, Lord Privy Seal (5 yrs, 10 mo.)
Stanley Baldwin (1923): President of the Board of Trade, Chancellor of the Exchequer (2 yrs, 1 mo.)
Ramsay MacDonald (1924): none (because he was the first Labour PM)
Neville Chamberlain (1937): Health Secretary, Chancellor of the Exchequer (11 yrs, 3 mo.)
Winston Churchill (1940): President of the Board of Trade, Home Secretary, First Lord of the Admiralty, Chancellor of the Duchy, Minister for Munitions, Air Secretary, War Secretary, Colonial Secretary, Chancellor of the Exchequer (18 yrs, 2 mo. - greatest number of offices and longest period of time (32 years) during which held, as well as 2nd on the all-time most experienced list)
Clement Attlee (1945): Lord Privy Seal, Dominions Secretary, Lord President of the Council (5 yrs)
Anthony Eden (1955): Minister without portfolio, Dominions Secretary, War Secretary, Foreign Secretary (12 yrs)
Harold Macmillan (1957): Air Secretary, Housing Secretary, Defense Secretary, Foreign Secretary, Chancellor of the Exchequer (5 yrs, 5 mo.)
Sir Alec Douglas-Home (1963): Dominions Secretary, Lord President of the Council, Foreign Secretary (8 yrs, 6 mo.)
Harold Wilson (1964): President of the Board of Trade (3 yrs, 7 mo.)
Edward Heath (1970): Labour Secretary, Lord Privy Seal, President of the Board of Trade (5 yrs)
James Callaghan (1976): Chancellor of the Exchequer, Home Secretary, Foreign Secretary (7 yrs, 9 mo.)
Margaret Thatcher (1979): Education Secretary (3 yrs, 9 mo.)
John Major (1990): Chief Secretary of the Treasury, Foreign Secretary, Chancellor of the Exchequer (3 yrs, 5 mo.)
Tony Blair (1997): none
Gordon Brown (2007): Chancellor of the Exchequer (10 yrs, 1 mo.)
David Cameron (2010): none
Theresa May (2016): Home Secretary (6 yrs, 2 mo.)