Gordon Brown yesterday passed a crucial test in his bid - which at 12 years is probably the longest power bid in political history - to take over as the next Labour Party leader, and thus become the next Prime Minister.

His tenth Budget, which he said he was "honoured and privileged" to deliver, clearly won the support of Labour back-benchers who waved their order papers and cheered with gusto after one hour and one minute of listening to the Chancellor splashing billions of pounds around the economy.

His confident performance, for a while, diverted the spotlight from the murky loans-for-honours row which is now bedevilling the Labour Party.

It was just the tonic they needed. But as banknotes rained down from the heavens, Mr Brown was careful to reassure those who wondered where all the money was coming from that not a penny was being spent that did not comply with his mysterious "fiscal rules" which he regularly and gravely vowed he would never breach.

Mr Brown, not noted as a comedian, started with a joke. He said that the last person to deliver ten Budgets was Nicholas Vansittart in 1822, in preparation for his next important position in Government.

A brief and unnerving pause. And then, with comic timing which would have done credit to Tommy Cooper, he blurted out "Chancellor of the Duchy of Lancaster" - a punchline which had the Chamber in fits.

Even the Deputy Prime Minister, John Prescott, who otherwise sat like a pudding through the Budget, seemed to get the joke.

Research has shown that when Vansittart retired as Chancellor, it was said of him that his views and statements could never be understood and that his opponents charged him with "wilful mystification" - a charge which one Tory MP said cruelly today, might apply to Mr Brown himself.

But Mr Brown was by no means as dour yesterday as his reputation suggests. Even the Tories managed a smile when he announced that, "in anticipation of World Cup success this summer", he was freezing duty on Champagne.

And in another example of his untypically chirpy mood, he spoke of his pledge not to extend VAT on children's shoes - "including flip-flops".

That word, which seemed to be directly addressed to David Cameron, the Tory leader, always reduces politicians to gales of laughter.

However, it was Mr Cameron who shamelessly dishonoured a pledge solemnly given. He had told the world, on election to the job, that there would be no more Punch and Judy politics.

Well, Mr Cameron revved his voice up to a stentorian decibel count, bellowing like a bull, and raining verbal blow after blow on Mr Brown, denounced him as a "fossil-fuel Chancellor", "a road-block to reform", "a politician completely stuck in the past" and "an analogue politician in a digital age".

Connoisseurs of parliamentary knock-about will be relieved to hear that Mr Cameron has restored Punch and Judy to their rightful place.