And so the 'quiet man' goes out with a bang.
In fact, no, it was an almighty explosion: The Conservative Work and Pensions Secretary has left office in a manner not seen since the resignation of Geoffrey Howe - in fact it makes Johann Lamont's departure as leader of Scottish Labour look sheepishly polite.
Timed to inflict maximum damage on the Prime Minister and the Chancellor, the former Tory leader has blown apart what is supposed to be our normally chirpy, cheery Chancellor's big week, and staged an almighty interruption to the Second Lord of the Treasury's continuous audition for leader of the Conservative party: It's less Joan Crawford and Bette Davis, more Kim and Aggie of How Clean Is Your House fame. Oh the drama!
It is well known that Mr Duncan Smith and Mr Osborne have not had the easiest of relationships. Now laid bare for all to see, Smith saw himself as the great reformer of welfare and Osborne was the schoolboy bully strutting across Whitehall and pinching the DWP Secretary's lunch money. The Bedroom Tax? JSA cuts? Sanctions? It was George's fault, Miss.
Of course no one is buying the line that the reason for his departure is the way that the Treasury has been forcing his hand over welfare cuts for the past six years - not wholly anyway. Whilst there is some plausibility in the view that he's not happy with how changes to Welfare have been packaged by the Chancellor - although the PM rejects this - his frustrations over the Government's approach to Europe are probably his primary motivations. Oh how we've missed a Tory rift over Europe - 'twas ever thus.
The worst part of the Tory soap opera - probably the worst since Crossroads - is that it inevitably alienates the electorate: at a time when the public ought to be engaged in a debate about Britain's place in the world - and, of course, upcoming Scottish, Welsh and English local elections - instead the party of government has chosen to go into self-destruct mode.
For me, as someone who wants Britain to remain in the EU, this is enormously frustrating. The only people I can see this benefiting are those seeking to take the UK out of Europe, and the more time we spend as mere spectators in this affair (know your place, boy!) the less time we have to make the case for Europe and shine a light on the woeful case of the Brexiteers. Even as I write this article, there are reports on the Today Programme that more Ministers are expected to head for the exit (the Whiethall one, that is). How depressing.
So if you were hoping to hear more about what a vote for remaining or leaving the EU would mean for job security; for our colleges and universities or for your rights at work, I'd hold off for now. The solipsism of the Parliamentary Under-Secretary for paperclip counting and whiteboards requires their moment in the Sun. Again, know your place.
And what of Labour in this whole affair? The Government is now deeply divided on three huge areas of policy: welfare, the budget and foreign affairs. That surely brings their ability to govern in the national interest into sharp focus, and sets up nicely a huge political opportunity for Labour's Jeremy Corbyn.
Well, yes and no: Yes, in that it is a huge political opportunity; and no because Labour are split on the three same issues - and much more - and the Rt. Hon. Gentleman for Islington North has an almost Mr Bean-like talent for missing and hitting the wall.
Last week's PMQs was the perfect example. Despite weeks of a continuing crescendo of internal Tory Warfare, a Tory budget only minutes away and a referendum on Europe only 100 days away, Jeremy chose to take the PM to task on air quality. Now I don't want to diminish the importance of this issue - in fact it is linked to my own work on the Transport Select Committee - but it showed an opposition leader who is leading with tin ears, and it is letting the country - the whole country - down. The Scottish National Party is now the only major party in Commons who are united on the big issues, and can be relied on to take the fight to the Tories at Westminster - and that is what we will continue to do.
There's only one winner in all of this, and he's got quite the hangover following a weekend on the Pol Roger: Boris Johnson. The Mayor of London hasn't even had to open his mouth yet he will have the biggest grin. Brace yourself. He's ready to enter, stage-right, any time now.