Lord Mandelson slid into the gallery in the Commons to watch PMQs, fresh from a morning of intense media activity. I must say that, as of yesterday, there is no doubt that Peter Mandelson is the Deputy Prime Minister in all but name. Indeed he may be more than that. Perhaps it is Gordon Brown who is the deputy now. Certainly their fates are totally intertwined.

I would love, just once, to be able to see the chamber as Lord Mandelson does. The man who behaves as if he is always being observed looks down on Gordon Brown proudly, eyes never leaving the scene below. Is he the great puppeteer? As Mr Brown answered his first planted question - Labour's propaganda is now brazen - I definitely saw Mandy's hands start to twitch.

The PM is as subtle as a bus crash. He answered the question about the new wonderful brilliant (I wasn't kidding about the propaganda) business loan scheme by emitting a slogan: “This is real help for business.” Then he added: “This is real help for small businesses.” And then: “It is real help for businesses.” And then: “It is real help for high-technology firms.”

Help! Had the PM, just back from his awayday Cabinet in Liverpool, been inspired by the great Beatles song? If so then, like an original 45, he was now stuck. After two more “helps”, I looked over at Lord Mandelson. Did his hands move? The PM sat down with a jolt.

Dave jumped up. “Planted question,” he announced in a voice that was full of cold. I waited for the verb. “Copied policy.” Was this a haiku? Was Lord Mandelson controlling him as well? Certainly it seemed so, for Dave was not as subtle, or as wily, as he can be. His performance was all Punch and no Judy and, if he is going to beat Gordon, he has got to have a bit of both.

Gordo hammered away, obsessively repeating his themes. The recession started in America. Everyone in the Universe is copying him. The Tories are out of touch. “It is a do-nothing policy! That is the Conservative Party!” shouted Gordon.

The battle was as familiar as a marital spat that always follows the same pattern. Dave savaged the VAT cut, branding it an “expensive failure”. Gordo flounced that, actually, a figure none other than Ken Clarke had endorsed it.

At the mention of Ken, the Labour backing chorus went into action. “Ken!” they cried as if Mr Clarke was their best friend. “Bring back Ken!” Mandy's lips (not to mention his hands) twitched. All of Westminster is obsessed with the Ken Clarke comeback story and Mandy is stoking it for all it is worth.

Why? The general explanation is that Mandy is backing Ken to return to the Shadow Cabinet because, actually, he doesn't want him back. Yes, I know. But in Westminster this is accepted as truth by people in the know. Mandy puts on a wonderful show, though. Earlier in the day he was singing Ken's praises to a select committee. “Bring back Ken!” he had cried. Could it be any coincidence that Labour MPs were shouting the same thing?

Bip. Bop. Bip. Dave and Gordo kept on trading insults about who was the more isolated. “The PM is completely isolated!” cried Dave. Gordo insisted it was Dave who was. “He is totally on the wrong side of the argument,” insisted Gordon. “If he wants to be outside the consensus about what needs to be done, let it be.”

Let it be. I think the Beatles must really have made an impact on the PM (Hard Day's Night could be his theme song). I yearned for Dave to start to sing a lamentation on Dear Prudence. Instead he accused the PM of “running around like a headless chicken”. The PM smiled his crazed grin in response.

Help! Up in the gallery, Mandy, hands quiet now, smiled.

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