GEORGE OSBORNE was greeted with almighty cheers from Tory MPs as he stood in at Prime Minister’s Questions.

Blue backbenchers, who, somehow, believe David Cameron to be insufficiently Thatcherite, can’t wait for the Chancellor to be crowned his successor to fulfil their cuts fetish.

But Osborne’s grip on his perceived birthright was dealt a blow yesterday when he came up against the son of Thatcher’s nemesis, Tony Benn, on his PMQs debut.

Shadow foreign secretary Hilary Benn hit the Chancellor with six serious questions on international affairs that stumped Osborne and silenced Tory backbenchers.

The link wasn’t lost on Osborne, who made matters worse by responding to Benn’s first question about terror group Isis with a joke about his family.

Oozing insincerity, he said Benn senior would have been “extremely proud” to see his son leading Labour.

In reference to Jeremy Corbyn, he added: “On this side of the House, we’re extremely pleased to see there’s no Benn in the leadership contest but plenty of Bennites.”

There was a stunned silence in the press gallery, such was the surprise that Osborne would give such a crass answer to such a serious question.

What was being done to prevent British people joining Isis? Why won’t Britain take its fair share of Syrian refugees?

Osborne tried to atone for his misjudgment by attempting to give answers but stumbled over his replies.

Unmoved, professorial Benn pressed ahead with his forensic examination of the government’s chaotic foreign policies.

Backbenchers dutifully rose to read out soundbites handed to them about the “long-term economic plan” but the Tory script had been scuppered.

The only person more pleased than Benn tonight will be David Cameron.