Boris Johnson’s memoirs will be published in October, publisher HarperCollins has announced.

The publisher said the book, titled Unleashed, would be “honest, unrestrained and deeply revealing”, covering Mr Johnson’s time as mayor of London and as prime minister when it is released on October 10.

The former prime minister said: “I am honoured that HarperCollins is publishing my personal account of the huge realignment that took place in UK politics in the last 15 years – and what may lie ahead.

“So stand by for my thoughts on Britain’s future to explode over the publishing world like a much shaken bottle of champagne.”

In January 2023, Mr Johnson’s register of interests revealed he had received a £510,000 advance for his memoirs, well above the £7,674 advance his successor Liz Truss received for her 10 Years To Save The West.

Since quitting Parliament last year after being found to have misled the Commons over Partygate, Mr Johnson has continued to tour the speaking circuit and write a column for the Daily Mail.

More recently, he has endorsed several Conservative candidates in the General Election and put his name to letters sent to thousands of voters warning them not to vote for Nigel Farage’s Reform UK.