When Ed Balls secured the job of shadowing Theresa May as home secretary, the groans from her advisers were audible.

Ms May is no doubt delighted she will no longer have to face this formidable political operator across the dispatch box. George Osborne will be less thrilled.

Alan Johnson, a former postman, may have had a modest enough background to cause a mild sense of embarrassment for the old Etonians on the government front bench, but Mr Balls has the firepower to make them squirm. As Alastair Campbell, the former Labour spin doctor, said last night: “Ed Balls is the replacement Osborne did not want.”

For Mr Balls – so close to Gordon Brown that one colleague quipped it was difficult to know where “Ed finished and Gordon began” – the promotion is a return to the natural order of things after he was passed over in favour of Mr Johnson.

The punchy ex-Financial Times leader writer has already done more to shape Labour’s response to the coalition’s austerity drive than other senior party figures, putting together a cogent critique of making savage cuts while economic recovery is fragile.

“The country knows you don’t have to do it this way,” he said on Thursday night.

Mr Osborne will make much of Mr Balls’s Brown connections to claim he was the man who got Britain into its current financial mess. Michael Fallon, the Conservative deputy chairman, said the appointment “beggared belief. . . Labour has learnt nothing”.

Another worry for Ed Miliband, Labour leader, is Mr Balls’s reputation as a political bruiser, used to having his own way while at the Treasury to the fury of Number 10.

The new shadow chancellor vigorously rejects accusations of bullying, despite the departure of several officials during the Brown-Balls Treasury years. While his television appearances are often edgy, in person he is approachable and does not appear hampered by a monstrous ego. He seems at ease whether talking to leading economists, trade unionists or schoolchildren.

Despite the long-standing antipathy of Blairites, Mr Balls insists he is not a natural “statist”, pointing to his championing of independence for the Bank of England. He is also proud of cooking up a deal with Mr Brown in the back of a taxi to keep Britain out of the euro.

After being elected to parliament in 2005, he was a junior Treasury minister before becoming education secretary during the ill-starred Brown premiership. He gained a reputation at the department as a highly political micro-manager – but also as someone who knew how to run a ministry.

As Ms May’s shadow he has retained his fearsome levels of energy, repeatedly pinning down ministers over their plans to slash police numbers. He will relish his time at centre stage as he tries to do the same to Mr Osborne.

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