Royal Bank of Scotland is to fit proximity-payment readers into 25 London taxies, allowing punters equipped with wave-and-pay cards to settle any fare under a tenner with a touch of the card.

Most London cabs accept credit cards these days, although some still resort to card-impression machines, but the percentage that has to be paid to the card-issuing company makes that ineffective for small amounts - taxies in Glasgow threatened to refuse chip and PIN transactions for less than £12, and charge passengers £1.50 for the privilege.

When one had to sign a credit card slip there was usually a blank line, headed "gratuity" into which one could write an amount for the tip. With chip and PIN that option disappeared, and it's taken a few years for terminals to start asking if you'd like to add a tip before entering your PIN. But with proximity payments there is no PIN, nor screen to interact with, so adding a tip becomes more difficult.

The 25 drivers involved in the pilot probably won't care, but if the system is to be more widely deployed, then perhaps a big red button marked "ADD TIP" is in order. But the cabbies still won't take you south of the river after midnight. ®

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