SIR Mark Sedwill is in line for a payout of nearly £250,000 after agreeing to step down as Cabinet Secretary early, a letter from Boris Johnson reveals.

The outgoing head of the civil service, who has also served as national security adviser to the Prime Minister, will receive a “compensation payment of £248,189” when he leaves the top Whitehall role later this year.

A letter from Johnson to Cabinet Office permanent secretary Alex Chisholm says the payment is “likely to be in the form of a pension contribution”, with the PM authorising the top-up “in consideration of his employment position” and “Sir Mark stepping down early”.

“You have advised me that this is regular and legal, and value for money to do so,” Johnson says.

“You have asked me to give my approval and make the final decisions because I am the responsible minister, and you report as a civil servant to Sir Mark and therefore cannot bring to bear the independent judgment required.”