The sale of a Downing Street visitors’ book from Margaret Thatcher and Sir John Major’s times in office has been postponed amid a dispute about its ownership, with the government claiming it is a piece of the nation’s history – and property. The red leather book contains the signatures of famous visitors including royalty and world leaders such as the former US president Ronald Reagan and Diana, Princess of Wales. The auctioneer has described it as “unique and historic”, with “a gilt-tooled front panel” and “gilt lettering”, and valued it at more than £10,000. The late queen and the Duke of Edinburgh signed the book during their visit marking the 250th anniversary of 10 Downing Street in December 1985. Other famous signatories include George HW Bush, the Princess Royal, Prince Abdullah of Saudi Arabia, the former prime ministers James Callaghan and Harold Wilson, and the heads of government who attended the G7 summit in July 1991. The book was put up for sale by a former civil servant in No 10, who said he found it among water-damaged boxes in a Whitehall basement more than 20 years ago, according to the auctioneer proposing to sell it. But the sale has been put on hold after the Cabinet Office said it was government property under the Public Records Act 1958. West London-based Chiswick Auctions has said it still intends to sell the book once ownership has been established, and claimed its client contacted No 10 twice – in 2017 and 2020 – to offer to return the book but received no response. While the auctioneer originally valued it between £10,000 and £15,000, it said it now has “every reason to believe” the eventual sale price might be higher due to a recent increase in interest. According to the auction house, the seller – who wants to remain anonymous – found the book after being given “permission and approval” to remove water-damaged boxes marked for incineration following a flood at 70 Whitehall. It was not until 2017 that he looked inside the boxes and, “to his amazement”, found the book packaged in tissue paper and bubble wrap. Valentina Borghi, the head of autographs and memorabilia at the auction house, said: “Having twice had no response from No 10, due to ill health and the cost of living crisis, my client has taken the very difficult decision to put the book up for auction in the hope of being able to meet some of those unaffordable expenses.” A Downing Street source told PA Media: “We will be taking steps to recover this crown property. The book is a piece of history – it belongs to the nation, not to an individual to be sold.” PA said it understood No 10 believed it had no record of the individual getting in contact in 2017 or 2020.