The public trial, called GetGo, was getting under way at its Express store on High Holborn in central London today after a pilot scheme for staff in Welwyn Garden City, Herts. Shoppers use a phone app to swipe a barcode as they enter. Sensors and cameras identify what they pick up, charging their accounts so they can just walk out. Kevin Tindall, the managing director of the chain's convenience store format, said: "We're looking forward to seeing how our customers respond."

       Age-restricted products will be kept in a separate part of the shop, with its own exit where staff will check shoppers' ID verification.

       A Tesco spokesman said the technology will save time "for those who want to pop in to pick up something for lunch or grab dinner".

       Aldi said last month it was trialling a supermarket without checkouts, for staff, also in London. Amazon Fresh, the online giant's first checkout-free store, opened to customers in Ealing, west London, earlier this year.

       Meanwhile, store chiefs hoping up for a bumper Christmas have started recruiting an army of workers.