People are asking if Boris Johnson will have the shortest term of any Prime Minister in Britain's history. Not counting one brief five-week caretaker prime ministership in 1834, which he's already outlived, Boris will have the shortest prime ministership in history if he's out by October 29th. But that person had also already served as PM once before (as had the caretaker); to be the shortest in total service, he could continue as far as November 18th.
But that's still cheating the record in a way, because both those PMs (Rockingham in 1782 and Canning in 1827) left office so quickly only because they died. To choose a PM who only served once and who left office for political reasons, the next step up is the previous record-holder for most hapless PM of all time: Lord Goderich, who served 131 days in 1827-8 and never actually met Parliament while in office. That would give Boris until the end of November to be bested by him; he's already even more hapless.
In other news, I was writing to a contributor to Tolkien Studies about typographical issues, and I started to write "in this case, house style trumps exact transcription," but even that innocent word is now so loathsome that I changed it to "house style is favored over exact transcription."