As the longest-reigning monarch, the Queen has kept up with many technological innovations in her time on the throne, and today she was finally introduced to the now-ubiquitous self-service till.

Touring a central London pop-up store celebrating the 150th anniversary of supermarket Sainsbury’s, the Queen was shown how millions of her subjects now pay for their groceries. 

And upon inspecting the device – and taking note of its security measures – the monarch quipped to a staff member: “And you can’t trick it? You can’t cheat?”

Despite never having seen one of the devices, the Queen’s question was remarkably apt – Britons are said to have stolen £3.2 billion worth of goods through automated tills, according to research by a voucher company.

The Queen made the comment during a trip to a pop-up exhibition in Covent Garden which replicated elements from one of Sainsbury’s original stores to mark the chain’s 150th anniversary.

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”.

The Queen met 33 members of Sainsbury’s staff during her visit, before unveiling a plaque and cutting a cake to commemorate the milestone birthday.

They included Damien Corcoran, who showed the Queen the stores’ modern technologies, including the till.

A former Army officer, Corcoran said it was a great honour “to have held the Queen’s commission and then to have met her in person”.

Despite not holding a Royal Warrant for supplying groceries to the Queen’s household – an honour which resides with its rival Waitrose, among others – Sainsbury’s described Her Majesty’s visit as a “great compliment”.

Lord John Sainsbury, life president and former chief executive of the company, greeted the Queen and called her visit “very flattering”.

He said: “I’m proud to say that what the company has contributed over the years has made it worthy of it.

“Of course, it’s a great compliment.”