It's a well-known platitude that the enemy within can be the most lethal of all. This has certainly been borne out in recent politics - the coup attempts against Gordon Brown and dissent amongst cabinet ministers being a case in point.
Nor is this a new phenomenon - in 1993, the then prime minister John Major famously branded three unnamed cabinet ministers (thought to be Michael Portillo, Michael Howard and Peter Lilley) "bastards" for their scheming and backstabbing.
The Tories have been quick to lambast the divisions plaguing Labour, but are things really so rosy amongst the blues?
From the spectre of Maggie to Mad Nad, Boris to Ken - David Cameron is surrounded by troublemakers in his own ranks. In this week's New Statesman, we've put together the 10 who pose the biggest risk.
If it's true that you should keep your friends close, but your enemies closer, then David Cameron would do very well to keep these 10 very close indeed.