We've been under the impression that David Cameron first began to explore the idea of a coalition with the Lib Dems in those first few tentative days after 6 May 2010.
But a new book, Cameron: Practically a Conservative, suggests that Oliver Letwin, William Hague, Ed Llewellyn and George Osborne first met to discuss the idea as early as 18 April.
According to authors Francis Elliott and James Hanning, Cameron agreed to conversations about a hung Parliament among his top team but insisted "that he should be kept out of the discussions".
At Osborne's Notting Hill residence, the senior Conservatives looked at the Liberal Democrat manifesto, the Conservative manifesto and transcripts about everything Nick Clegg had promised should he come to power, the book alleges.
This would then become a very early draft of the coalition agreement, the authors say (in a Times extract today).
If true, it paints a fascinating picture for the Conservatives early election predictions. The idea that they were planning for a full coalition weeks before the election suggests that they were nowhere near as hopeful as they were stating publicly.
It also reinforces the idea that Labour started coalition negotiations with the Lib Dems on the back-foot. No such conversations are supposed to have taken place among senior Labour forces.