Retail Eyes has carried out the project for the past five years and won a three-way pitch to retain the 2010 contract.

The firm will carry out 18,000 mystery shopping trips around Subway’s 1,465 UK and Ireland restaurants to evaluate customer experience and store performance across a range of criteria including store environment, product availability and staff presentation and service.

Subway’s head of marketing Alex Cacouris said: “Getting our customer service right is vital if we’re to continue to remain competitive which is why we chose to stay with Retail Eyes. They really understand our business and have been consistent in working effectively with our franchisees to translate customer feedback into real business results.”