In view of the partisan, pro-Liberal Democrat implications of Hazell's claim, it is worth setting out why it was so dubious and so irresponsible. First, it implied that the Queen had taken a decision to intervene in British party politics in a manner which, had Hazell's report been well-founded, would been inconsistent with the role of a modern constitutional monarch. Second, Hazell's statement runs counter to past practice. I reported the crucial historical evidence from the events following the hung election of 1929 in my written and oral evidence to the Political and Constitutional Reform Committee of the House of Commons in March 2011. I wrote:

The example of 1929 — when a sitting premier headed the defeated party in a hung election as in 2010 — does not accord with the [Hazell interpretation]. The incumbent prime minister, Stanley Baldwin, was under no "expectation" and under no "duty" to delay his resignation. He "consulted constitutional experts who assured him that it was in the prime minister's hands to do as he chose". Baldwin duly went to Windsor Castle without delay to tender his resignation to King George V. [Keith Middlemas and John Barnes, Baldwin: a biography.]

. . . [According to] the formulation in a standard constitutional law text by A.W. Bradley and K.D. Ewing, "Where after an election no one party has an absolute majority in the House  . . . the Prime Minister in office may decide to wait until Parliament resumes to see whether he or she can obtain a majority in the new House with support from another party . . . or he may resign without waiting for Parliament to meet (as Baldwin did in 1929 and Heath in 1974). When he or she has resigned, the Queen will send for the leader of the party with the largest number of seats . . ." 

Only when the leader of the Opposition fails to form a government may the Queen, according to Bradley and Ewing, then initiate coalition discussions between the parties.

The main fruit for the Liberal Democrats of being able to play off the Conservatives against Labour was to secure a Conservative commitment to hold a referendum on electoral reform. In retrospect, it seems that Cameron was misled into thinking that Labour was prepared to offer this if he refused to do so. That is what Conservative parliamentarians were told. The only reason why the Liberal Democrat manoeuvre failed to achieve a far-reaching effect was the party's defeat in the referendum on the Alternative Vote of May 2011.