Meanwhile extraordinary new details of how Clegg negotiated the coalition deal with Cameron in the days following the election are revealed tomorrow by the Observer's chief political commentator, Andrew Rawnsley, in two additional chapters of his book, The End of the Party.
On the Tuesday after the election, Clegg rang repeatedly to beseech Brown to stay put, telling him: "Gordon, this isn't over yet." He also demanded more time to negotiate with the Tories.
"Time for what?" demanded Brown. "Unless you can tell me you've broken off talks with the Tories in favour of discussions with us, I'll assume you're going with the Tories. I can't wait any longer. I've got to go to the palace."
Clegg insisted that a deal with Labour was still in play. "I can't be rushed," said Clegg, before asking for another three hours. "I'll give you half an hour," Brown replied. Clegg rang again. "Can I have five minutes more?" he asked. "Fine," said Brown. "Five minutes." When Clegg rang back asking for another extension, he said: "Please don't resign. Please don't go to the palace." Brown was adamant. "You've made your choice. I'm not going to hold on."
Clegg persisted. "You can't resign," he said. "This is absurd."