The Sketch: All aboard Vince Cable's big sensible tax policies bus

What a skidpan politics has become. The big old bus has driven into Bournemouth with tyres smoking and engine screaming, the driver has flung the wheel round, yanked the handbrake for a wide, 180-degree turn and the Social Democrats in the back gargle with fear as they are carried off they know not where.

The daring manoeuvre has been executed with quite unexpected panache. It's almost professional. Hooray for the Liberals, frankly. Not only are they the most likeable set of MPs (being furthest from power they are more like people than politicians), they have a history of being first. They were first to make the environment an issue. First to argue for higher taxes and public spending, and now as the political cycle enters a new phase, first for lower taxes. This may be the first time in years they've got the timing right.

Conference hero Vince Cable put it all together in a superb piece of coalition-building. It was the deftest speech of any importance in the past decade, and it has now established a truly radical proposition in public discourse: income tax starting at 16p in the pound.

The enemies? Tax dodgers, Tesco, Tories. Failed executives with vast kiss-off payments. Grotesquely complicated benefit systems. Insane IT projects. Nuclear power companies. Government hubris. Quango heads making more than £100,000 a year; they have to reapply for their jobs and (to gasps), "Those allowed back would take a cut in pay and public sector pension entitlement."

The heroes? People on the minimum wage. Social landlords. Liberals.

And the new mechanism for social justice, for "a fairer society"? A massive reduction in tax paid by the poorest earners, and the possibility of a net reduction in the tax burden. That's astonishing. It says that state spending is not the full and final answer to social problems.

To be fair, it's hardly come out of the blue. Cable has been saying for some years it's unfair for the lowest paid to be paying proportionately more in tax. But only now that the Orange Book (David Laws' liberal vision of the Third Way) has completed its journey from heresy to orthodoxy has the message become real.

And Vince, with his gloomy, unimpressible manner, manages to pitch values of austerity, restraint and sobriety in a way that fails to deter the extravagant, the incontinent and the frankly intoxicated. I speak for myself, naturally.

If this shifts poll ratings away from Labour it's going to make things very difficult for Gordon Brown. It strikes him deep in his most vital parts.

"Let the work of change begin," as he once said himself.

simoncarr@sketch.sc