George Osborne, the Shadow Chancellor, said that he had hired a handwriting expert to analyse Mr Brown’s character — and the conclusions were far from flattering.

It was Mr Osborne’s revenge for a typically ferocious assault on the Conservatives’ economic policy launched by the Chancellor when the two clashed in the House of Commons last month.

Mr Brown taunted the Tories over a document published on the party’s website, apparently indicating that a policy group headed by John Redwood, the right-wing Conservative MP and former leadership challenger, wanted to abolish consumer protection for mortgages, pensions, insurance and credit cards.

During the excitement of their clash at Treasury Questions in the Commons, Mr Brown hurled a document from the Conservative’s policy group across the dispatch box at the Shadow Chancellor.

To the delight of Mr Osborne, once the hubbub had subsided he noticed that the Chancellor had jotted some brief handwritten notes on the document in his characteristic giant, markerpen scrawl.

Although amounting to just 14 words, the Conservatives believed that they had enough to extract their revenge and gave the note, without identifying its author, to Sarah Mooney, principal of the London College of Graphology.

Ms Mooney’s considered opinion ran thus: “The writer is not shy. The writer shows unreliable and poor judgment. The writer was not in control of their emotions and instincts at the time of writing.

“There are signs that the writer is someone who does not like to give a clear-cut image of himself. There are signs that the writer can be evasive.”

She was careful to say that the sample of 14 words, with no signature, was insufficient information on which to base a graphological analysis of the handwriting.

But the professional opinion she did give carried echoes of the infamous criticism of Mr Brown, made anonymously during a period of his episodic feuds with Mr Blair in 1998 but widely attributed to Alastair Campbell, that he had “psychological flaws”.

The words themselves appeared to be prompting notes scribbled by Mr Brown while sitting on the front bench in the Commons waiting for his moment to launch his attack on the Conservatives.

In large writing, in capital letters, he wrote: “SOME HAVE [illegible] + PENSIONS / MORTGAGES / INSURANCE / SHARES / BANKING”.

Two months ago Mr Osborne triggered a row when he joked at a fringe meeting at the Conservative Party conference that the Chancellor was autistic.

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