Alternative Vote is not Proportional Representation. And to be very clear, liberal democrat MPs, including Nick Clegg, were photographed with signed papers saying that if they were ever in government they would abolish tuition fees. A cynical ploy to win university constituencies.

That said, the country was reeling from the 2008 banking crisis, that even with a competent PM in Brown (despite his 'ignorant woman') comment was leading a Labour government into its 14th year. Even then David Cameron only won a minority government. If the lib dems hadn't backed the Tories into office, very likely we would have seen a second general election within short order.