'Dynamic currency conversion', where you're given the choice between paying in pounds or in the local currency when using ATMs or card machines abroad, is marketed as a way for travellers to know what they're paying in their home currency – but it can lead to people paying extra unnecessarily.

This is because if you choose to pay in pounds, the currency conversion will be done by the retailer's bank, and you're likely to get a poor rate.

But if you pay in local currency, your card will do the conversion, and if you've got a top overseas travel card you're guaranteed near-perfect exchange rate. It's why Martin always says to pay in euros rather than pounds.

From Friday 12 April, travellers with prepaid multicurrency cards using the Mastercard network, such as WeSwap, FairFX and Caxton, will no longer be offered the choice of paying in pounds. Instead, their transactions will automatically be processed in the local currency, which should mean they get a better deal.

Travellers spending on Mastercard credit and debit cards will be offered the choice between pounds and the local currency as usual.

See our Prepaid Travel Cards and Travel Credit Cards for full info on the best ways to spend abroad.