And while the business has grown into a 100-strong franchise network, the basic principles that made its self-service boxes profitable back in 1991 continue to do so today.

With an 'honesty' box there is no personal contact with a vendor at the time of purchase, nor is there a mechanical vending process in place. Customers are relied upon to leave the correct change in return for the tempting snacks on offer.

Sales director Matthew O'Neil said: “People ask me whether customers really do put the money in the box, and seem genuinely surprised that an honesty system works in this day and age.

Most customers are decent, and honest enough to leave the exact amount in a fair exchange for the snacks they take away.

We also have franchisees who are well into their third term - people who have been successfully trading for more than twelve years. And why would anyone stay in business that long if that business didn't work?”

Information: 023 9241 5000 www.sitb.co.uk