INSIDE THIS FAT, waddling tome I suspect there is a slimmer, fitter book trying to escape. A tie-in with Andrew Marr’s BBC TV series, it reads as if, freed from the constraints of a tightly edited script, he has shovelled in all the sweepings from the cutting-room floor. The result is a 600-page volume that can feel a bit thin on ideas.

Marr begins “What follows is a story of the failure of political elites” – a good vantage point from which to survey Britain since the war. But why might they have failed? The blurb offers his clearest explanation that “the great political visions, and rival idealisms [of Labour and Tories] . . . came to be defeated by a culture of consumerism, celebrity and self-gratification”.

Yet the long story that Marr tells hardly sustains his notion of “great political visions”. It illustrates the narrow-mindedness and conservatism of British politics – from the supposedly radical postwar Labour Government, revealed as largely a collection of Little Englander neo-puritans “far keener on the Empire than one might expect of socialists”, whose policies and personal health were soon exhausted, to Margaret Thatcher’s governments, which Marr flatters as “the British Revolution” before reminding us that the 1979 manifesto hardly mentioned policies such as privati-ation, which became the pragmatic Thatcher’s hallmark almost by accident. Idealism didn’t come into it.

Marr is right to conclude that “politics shrivelled”, until we were left with only Tony Blair’s Cheshire-cat smile. But it was not so much “the defeat of politics by shopping”, more that the British go shopping when there is nothing more interesting to do. The culture of consumerism and celebrity fills the gap where our public and political life ought to be.

Like many a leftish intellectual, however, Marr can barely suppress his distaste for the vulgar indulgence and “self-gratification” of the masses today, sympathising with postwar Brits who, he imagines, would feel “shock and disgust” at our “gross wastefulness”.

In the end he seizes upon global warming as the cue for the return of “true politics . . . in a way the British of the Forties would have recognised”. So bring back rationing! – of carbon, rather than sugar, but it’s the miserabilist thought that counts. One difference with the Forties is that Labour’s political horizons have sunk from conquering the “commanding heights of the economy” to scraping the bottom of the compost heap.

In the spirit of eco-austerity, Marr half jokes that he will not tell the boring history of the Blair-Brown rivalry in order to save trees. He might have done himself and his readers a favour by sparing a few more.

Macmillan, £25; 629pp £22.50 (free p&p) 0870 1608080

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