It is a measure of my increasing cynicism about the political process that the resignation of Mr Purnell has me casting about for an ulterior motive. I ask myself, what's in it for him?
Unlike mesdames Smith and Blears, he was not facing the prospect of defenestration from the cabinet. Indeed, if you believe the gossip, he had been offered Balls' post as children's secretary, arguably a promotion of sorts. Furthermore, the Prime Minister had gone out of his way to dismiss the speculation about his alleged dodging of capital gains tax on the sale of his London flat.
Nor has there been any pretence about wanting to spend more time with his family or reconnecting with his labour roots. No, it was a straightforward 'Gordon, you're not up to the job' (I paraphrase, but only slightly).
Furthermore, while the Prime Minister may be wounded, he is still the biggest beast in the jungle and well capable of wreaking a terrible revenge. And the Party still retains more than a vestigial attachment to loyalty, which may make Mr Purnell's life in his constituency or on the back benches less than entirely comfortable.
Finally, as the assassin who wielded the knife, Mr P must be aware that his chances of succeeding to the leadership of whoever replaces Mr Brown must have diminished to almost non-existent.
Could it possibly be - just possibly - that Mr P acted as he did because he thought he was doing the Right Thing?