Britain's top civil servant helped end Liz Truss's premiership, it is claimed.
In an example of the power wielded by the Whitehall 'Blob', Cabinet Secretary Simon Case is said to have written a memo that helped seal her fate as the shortest-serving prime minister in history.
According to an account by one of Miss Truss's biographers, the top mandarin told her to abandon her economic policies because of the chaos they were causing in the financial markets.
Soon afterwards she was forced to U-turn on her plan to cut corporation tax, and a week later resigned after Tory chairman Sir Graham Brady told her she could not continue in Downing Street.
James Heale wrote in the new issue of The Spectator: 'I understand that last year it was Simon Case, the head of the civil service, who wrote Liz Truss a memo telling her to abandon her economic agenda on the grounds that it was causing market chaos.
'From that moment, her premiership was doomed. It was a civil servant, not a Cabinet delegation or opposition leader, who sounded the death knell for Trussonomics.'
A source confirmed to the Mail tonight: 'As I understand it, the Cabinet Secretary went to see the PM and gave her advice on the need to change course.' However, the insider said that given the urgency of the situation it was a face-to-face meeting, following warnings from the Bank of England and Treasury.
Sources close to Miss Truss declined to comment but did not deny the incident had occurred. Ms Truss took over from Boris Johnson on September 6 last year - but resigned just 45 days later.
She and her chancellor Kwasi Kwarteng produced a controversial and radical plan for growth that he unveiled in a mini-Budget on September 23 featuring £45billion of tax cuts. But the financial markets reacted negatively. The value of the pound fell, and mortgage rates and the cost of Government borrowing soared.
Conservative MPs turned against Ms Truss.
She sacked Mr Kwarteng on October 14 and quit herself six days later, admitting she could not 'deliver the mandate' on which she was elected leader.