To set up the trial – the biggest of several in Europe – Visa teamed up with Spanish savings bank La Caixa and mobile phone company Telefónica, owner of 02 in the UK.

Around 1,500 local residents were chosen and Visa persuaded 500 retailers, from tobacconists to hairdressers, to accept the mobile payments, giving them adapted sales terminals.

Every participant was given an adapted Samsung handset that, to the untrained eye, looks exactly like any other smartphone. Embedded in the phone is a chip containing the user's bank card details – similar to the chip in a conventional credit or debit card. The phone also has a local transmitter to allow it to communicate with the retailer's sales terminal.

To make a purchase, the salesperson keys in the amount to be debited and, if it is less than €20 (£17), the buyer places their phone next to the terminal. The bank card details are transmitted to the terminal to make the payment and if successful, a tick appears on the phone's screen. For items costing more than €20, the process is the same except that a pin is required – input in the normal way. The amount is then debited from your account as though you had made a conventional card purchase.