Which Prime Minister is mentioned as an old Etonian?

David Cameron is the Prime Minister mentioned as an old Etonian because he attended Eton College, a prestigious boarding school in England known for its notable alumni, including many British Prime Ministers. In the context of British politics, being an "old Etonian" often signifies a connection to the elite circles of British society and education, which has historically influenced the political landscape.

Tony Blair, Gordon Brown, and Boris Johnson, while prominent political figures, do not share the same educational background of attending Eton. Blair attended Fettes College, Brown attended Kirkcaldy High School and the University of Edinburgh, while Johnson also has a connection to Eton but is not commonly recognized specifically as an old Etonian in the same context as Cameron, who was often associated with that elite status during his time in office.