Lib Dem Treachery?

For decades, Liberals and later , Lib Dems, canvassed for PR in this country. They were pleading for the opportunity to 'hold a would-be government to ransom' so that they could achieve this aim. Yet, look what happened when this scenario finally emerged. The Lib Dems sold out to the Tories for a referendum on - of all things - AV+. Nobody in their right mind would have voted for such a crazy system which few could even understand. This was the principal reason that AV+ was rejected.
Let me ask the question 'WHY?' It is the firm belief of this Blogger that the Lib Dems no longer wanted a fair PR system because THIS WOULD HAVE BROUGHT UKIP DRAMATICALLY INTO THE GAME. Sell out your so-called principles for unenlightened self interest? - You bet!