If the case is successful, consumers could potentially receive hundreds of pounds each – even if they don’t have a Mastercard. The legal action has already been going on for five years, including various appeals.

In September 2016, former Financial Ombudsman Walter Merricks launched proceedings against Mastercard for losses suffered as a result of illegal card fees.

It was the first mass consumer claim brought, following the European Commission’s decision in 2007 that Mastercard breached competition law by fixing default interchange fees as part of its payment card scheme between 1992 and 2007.

Merricks sought redress for UK consumers, stating that unsuspecting UK shoppers bore the brunt of these credit card fees through higher prices of everyday purchases whether they paid by cash or card. Mastercard’s fees were a significant cost for retailers that was then passed on to consumers through increased prices of goods and services.

The Competition Appeals Tribunal (CAT) has this week ‘certified’ the claim against Mastercard, which means the case can now move to trial. The judgement follows a hearing held this March which considered what could be included within the scope of the case and whether the case could proceed.

The next hearing is expected to take place in September or October.

Merricks’ class action case will represent all consumers who made purchases in the UK between 1992 and 2007, who were aged 16 or over, and had lived in the UK continuously for at least three months. However, the CAT has declined Merricks’ request to include deceased people in the claim.

Gareth Shaw, Which? head of money, said: “This is a really positive step for consumers. Which? has campaigned long and hard for an effective collective redress scheme which gives large numbers of people the opportunity to hold companies to account where they have been harmed by manipulative business practices.

“This claim proceeding to trial could open the door for many other cases to follow suit – ensuring victims of anti-competitive behaviour can get the justice they deserve.”