When Mr Brown’s hands thumped the air for emphasis, this Cabinet minister’s head nodded in perfect time. It was not Tony Blair, but Alan Milburn, whom Mr Brown has many reasons to dislike and distrust.

The new Chancellor of the Duchy of Lancaster may have usurped Mr Brown’s role in the next election campaign, and, according to some new Labourites, his title as heir apparent. But if the Chancellor’s speech was a closely scrutinised test of his loyalty to Tony Blair, in the row of seats behind him was a little-noticed but fascinating trial of Mr Milburn’s loyalty to Mr Brown.

It was a virtuoso performance, with not a yawn nor a scratch, let alone the appearance of a pair of rabbit ears over his colleague’s head.

The 35 minutes that Mr Brown was on his feet began perfectly, with Mr Milburn asking to shuffle up from his seat on the edge of the platform and sit three places from the Prime Minister. As soon as the speech began, Mr Milburn kept his eyes narrowed in a hunter’s gaze fixed on Mr Brown, while his head bobbed almost continuously.

The impression that Mr Brown was Mr Milburn’s puppeteer should not, however, be taken as any reflection of their private feelings, said Peter Marsh, co-director of the Social Issues Research Centre in Oxford. “This is the life of a politician,” he said. “Milburn must have known he was being watched, and he took pains to look attentive although not entirely pleased with the world, his mouth turned down.”

On many occasions Mr Milburn struck a thoughtful pose, with his finger over his mouth as if to button his lip, especially during the many sections of Mr Brown’s speech that crossed into his own brief to re-focus the party for the next election.

Mr Milburn’s real audience, however, may have been three seats away. On the handful of occasions his eyes left Mr Brown, they were mostly to check the reactions of the Prime Minister. He discreetly muttered something to Patricia Hewitt to his right. And then he made a strange flicking action with his hands, as if to brush away a troublesome fly.

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