It probably isn't brilliant politics. It will do him personally not one iota of good, and the manner of it cannot be called distinguished. Yet there comes a time in the life of the perpetually abused wife when, damn the consequences, all you want is to see her throw acid in the abuser's face. And so today we deploy one of the unlikelier four-word phrases in the language, and declare this: well done, Nick Clegg.

If there was a petulant tone to his announcement that he would kill the boundary changes in revenge for the Tories slaying constitutional reforms less palatable to them than being gifted up to 20 extra seats, small wonder about that. Clegg has delivered his version of the Peter Finch soliloquy in Network. Nick's mad as hell, he isn't going to take it any more, and about bleeding time, too.

He could and should have done this long ago, and might have done but for entering this wedlock with the heart-rending, doe-eyed naivety of the 19-year-old Diana. He actually seemed to believe, bless him, that this was one of those establishment-arranged marriages in which love, given half a chance, might blossom.

But even while he and David Cameron were honeymooning in the Rose Garden, there was a third element in this marriage. Playing Camilla was a Conservative right wing resentful at its usurpation by a virgin child bride, and regarding the marriage licence as not worth the paper on which the Coalition deal was printed. Bamboozled by its lunatic arrogance into misreading a truly hideous election result as a ringing mandate, it set out to wreck the marriage. And so, abetted by a David Cameron too feckless to tell it where to go, it did.

The maltreatment of the Liberal Democrats has been cushion-bitingly embarrassing to observe, if less so than Clegg's failure until now to resist it. In the days ahead, a torrent of cant will paint him a traitor for reneging on his support for redrawing constituency boundaries, though I can't recall the Tories savaging him for reversing his opposition to hiked tuition fees. When it comes to picking cherries from the tree of treachery, these people are champions.

The decisive act of betrayal in this macabre tale came not this week, but last year when the Prime Minister tacitly backed the character assassination of Clegg during the AV referendum campaign. It was sneakily brutal of him to do this, and a less docile creature than his deputy would not have tolerated it.

Instead, with the sorrowfully Diana-ish air that has come to cling to him, he rolled himself up into the foetal-doormat position and virtually invited the Tories to trample over him again. They did. However imperfect his House of Lords reforms, the bloodlustful way the Tory benches tore them apart bespoke something less high-minded than a principled defence of the nonsensical collection of conventions formally known as "our constitution". They wanted to give the Lib Dems another hiding for not being grovellingly grateful for a few ministerial cars, and for insolently imagining that the sharing of office implied the sharing of power. Like Diana, Clegg's role was to look innocent and pretty, and humanise Cameron without presuming himself to be a distinct personality in his own right.

Finally, he has cottoned on to the clichéd truth that traitorous bullies, even those like Mr Cameron with smiles on their faces, respond only to being bullied back. It is too late to save Clegg now. Whether he packs his suitcase or stays in a relationship of enough passive-aggressive horror to make the Fawltys' look blissful is almost an irrelevance. It is more comfortable to stay, the accommodation and food being far better than in the Erin Pizzey Home For Abused Political Wives, but the continual humiliation must be excruciating. Either way, he has no future, so that fine judgement brings to mind Alan Bennett when asked if he was straight or gay. You might as well ask a man dying of thirst in the desert whether he'd prefer Evian or Perrier.

All of which is a long-winded way of saying that the sensible response to Nick Clegg's suicidally belated declaration of war is to strip away any pretence of analysing it in tactical or strategic terms (though Ed Miliband will be beside himself with joy), and react on an instinctive human level.

Clegg has made atrocious mistakes in the past two years, and to some extent been the enabler of his own abuse. This is not one of those occasions. Even those of us who have long wished him out of our misery, and replaced by a Vince Cable who'd never have stood for the betrayal of the letter and spirit of the Coalition Agreement in the first place, must congratulate him for lashing out now. Politics is the nastiest combat sport on earth, and better learn this too late than never at all.

There was nothing magnificent in this undisguised act of vengeance, but finally Clegg is playing the game as it has to be played. C'est ne pas magnifique, to reverse Marshal Canrobert about an earlier leader who led his troops into the valley of death, mais c'est la guerre.