Builders renovating a foyer in the National Gallery in London were left stunned when they demolished a false column and discovered a letter hidden inside, written more than 30 years ago. Eerily, the letter, written by Lord John Sainsbury in 1990, had predicted that the structure would be destroyed - and thanked the builders for doing it.

Lord Sainsbury (Preston Candover), chairman of the supermarket chain for 23 years, left the prophetic letter after a dispute over the ultimate design of the National Gallery's Sainsbury wing. This extension of the London gallery was entirely funded by John and his two brothers, Simon and Timothy, but the life peer disagreed with postmodern architect Robert Venturi's decision to insert two false columns into the wing's foyer.

During a 2023 renovation of the wing, the gallery decided to open up the room and remove these non-load-bearing columns. A decision that Lord Sainsbury, who died in 2022 at the age of 94, said he was "absolutely delighted" by.

The letter, written and signed by Lord Sainsbury in July 1990 before being hidden inside the false column, has now been preserved in the National Gallery's archives. Stamped with a Sainsbury's letterhead, the prophetic message starts: "TO THOSE WHO FIND THIS NOTE."

The former supermarket chief's letter was protected by a plastic envelope before being encased in the columns, which he described as "unnecessary" and something the brothers would "live to regret." The wing was opened by Queen Elizabeth II less than a year later in 1991.

It continued: “If you have found this note you must be engaged in demolishing one of the false columns that have been placed in the foyer of the Sainsbury Wing of the National Gallery. I believe that the false columns are a mistake of the architect and that we would live to regret our accepting this detail of his design.

“Let it be known that one of the donors of this building is absolutely delighted that your generation has decided to dispense with the unnecessary columns."

The Sainsbury's brothers grew their enormous wealth, which they used to donate to cultural and political causes throughout their lives, through the supermarket business they inherited from their great-grandfather, who opened the first shop on Drury Lane in 1869. During John's time at the helm, the company's value ballooned from £117 million to £8 billion, after floating the company on the London Stock Exchange, while the family retained overall control.

Neil MacGregor, the National Gallery's director during the wing's construction, explained to the Art Newspaper why he agreed with the installation of the foyer's false columns at the time. He said: “Although there were drawbacks, Venturi had a coherent idea of the organic link between entrance hall, staircase and main galleries.

"I felt that, on balance, we should let the architect be the architect.” But just three decades later, the prestigious national art space decided to undertake an £85m renovation project - part of which was to knock down both of the false columns.

Lord John's widow Anya said: “I was so happy for John’s letter to be rediscovered after all these years, and I feel he would be relieved and delighted for the gallery’s new plans and the extra space they are creating.”