Today, the backbencher and MP for Clacton Douglas Carswell announced he would be defecting from the Conservative party to join Ukip. Aside from being a vocal critic of much of what the Tory leadership has and hasn't done in power, he is also known to be forthright in his disagreements with David Cameron.
Never was this tense relationship plainer than in 2012 when the two clashed in the Commons during a particularly fiery PMQs session.
Carswell asked the PM about one of his pet subjects, the role of the civil service. He asked Cameron why he had insisted what Carswell tags the "Whitehall machine, the Sir Humphrey factor" wasn't frustrating reform, only to say a few weeks later that Yes Minister was true to life.
The PM replied, rather pointedly: "I think the Hon Gentleman does need a bit of a sense of humour."
"I can do humour, but right now they are not laughing about the budget in Clacton, they're not laughing about the lack of economic growth in Clacton, there not laughing about 20% VAT hike on static caravans in Clacton... I didn't feel it was an appropriate day to do gags in the chamber."
Watch the put-down here: