The entirety of Brexit and referendum all started with a promise that he never thought he'd never have to keep when he offered it as a bargaining chip during the 2015 election. He was sure that he'd end up with another coalition government and so lied throughout the election. Then, once the election was over, instead of manning up and just admitting the truth that the referendum was not something he supported or would ever personally uphold if he was in power, he just rushed ahead with it leading to the most chaotic and shambolic mess you've ever seen with both sides making an absolute mess of their respective campaigns (with his own begin among the worst of them).