While being given a demonstration of a self-service supermarket till and its weighing scale system on Wednesday, the Queen asked: “You can’t cheat then?.”
She was also shown a new shopping app, which she called “an interesting tool”.
The supermarket opened its original store in Drury Lane in 1869, selling butter, milk, and cheese.
During her visit, the Queen also got the opportunity to see an original ration book from the Second World War, and reflected on her own experiences of food shortages.
She said: “As a Sunday treat we had some sweeties, but we were lucky we had a farm.”
There was also a demonstration of a shopping basket from the 1950s, containing a herring paste that the Queen labelled as “ghastly”.
When the porridge and oranges of six decades ago were contrasted the avocados and ready meals of 2019, she remarked “tastes have changed”.