| Prime Minister | Government | SpAds |
| Kings and Prime Ministers | Various governments through the ages | Without any formal system, Kings, Prime Ministers and individual Ministers brought in particular advisers. Such advisers were friends, cronies, colleagues. Until 1920, personal and political appointees were commonplace serving in the Prime Minister’s private office |
| Harold Wilson | Labour government, 1964-1970 Labour government, 1974-1976 | Formalised SpAd-specific roles and job titles Appointed as temporary civil servants, “experts” such as Thomas Balogh. The term “Special Adviser” (SpAd) commonly used for the first time in 1975. Ministers allowed to appoint SpAds on a regular basis. 38 SpAds in 1974, dropped to 24 in 1976. |
| James Callaghan | Labour government, 1976-1979 | Surrounded himself with shrewd academic advisers. Reduced number of SpAds from 29 to 24 |
| Margaret Thatcher | Conservative government, 1979-1990 | Initially hostile to political advisers, as opposed to expert advisers 20 SpAds in the early days |
| John Major | Conservative government, 1990-1997 | 38 SpAds in 1997. |
| Tony Blair | New Labour administration, 1997-2007 | Between 70 and 84 SpAds during his office (70 in 1998; 82 in 2004). SpAds increased in numbers; greater influence over career civil servants; perceived privileged position as policy shapers. Two SpAds, Jonathan Powell and Alastair Campbell, were given executive powers over civil servants. |
| Gordon Brown | New Labour administration, 2007-2010 | 73 SpAds in 2008. 74 SpAds in 2010. |
| David Cameron | Conservative and Liberal Democrat coalition government, 2010-2016 | 98 SpAds in 2013. 103 SpAds in 2014/5 (increase was following the decision by the then Deputy Prime Minister, Nick Clegg, to expand his political operation). 92 SpAds in 2015 reduced to 83 (one SpAd in Downing Street and 11 from the key Whitehall departments). |
| Theresa May | Conservative government 2016-2017 | 88 SpAds in 2017. |