M&S finds itself in trademark disputes more than other supermarkets because it has developed in-house brands that “rival supermarkets would die for,” says a grocery source.

The well-regarded own-brands are a legacy of the fact M&S only started selling branded products in its food stores in 2009.

For decades, it relied on designing its own unique products that could draw customers away from stores selling household names such as Heinz and Kellogg’s. It lent heavily on innovation, developing its own brands to draw in customers.

“Percy Pig is one of our ‘hero’ brands and we own trademarks to protect it,” the retailer said in a letter to Vincineti, sent the same day the ice cream went on sale. 

“We risk losing those trademarks (and more importantly to us, consumers will no longer be confident Percy Pig-branded products originate from M&S) if we do not take steps to stop others from using them without our permission.”

Ms Catton, who started her career as an M&S food developer and was the creator of its Percy Pigs line, says coming up with something new and different is key.

“At many of the supermarkets, it all becomes a lot of the same thing,” says Catton, now a consultant. “They’re all selling Cadbury’s, so the question is how you differentiate from Waitrose or Tesco.”

She says it is frustrating when other supermarkets launch their own, similar versions to M&S’s well-known characters.

Protecting its brands has only become harder with the expansion of Aldi, which is well known for developing its own products that look eerily similar to higher priced rivals.

M&S has accused the German discounter of launching knock-off versions of its “Colin the Caterpillar” cake and its Christmas glowing gin bottles. M&S reached a settlement deal with Aldi in the first case and won the second case. Aldi is appealing the light-up gin decision.