It seems impossible to find a definition of mayonnaise that does not refer to eggs as a key ingredient. The name is reputed to come from the town of Mahón on the island of Minorca. Local tradition recounts that it was originally known in Spanish as salsa mahónesa.

Of course, had it been a French product associated with a location such as Champagne, it is likely that anyone producing mayonnaise without eggs would have been obliged to use a different name. The investment in protecting Champagne as an incredibly valuable French regional brand has been, and still is, huge. It is now a £5bn industry.

So we come to the legal spat in the US between Unilever, the maker of Hellmann's, known for its numerous varieties of mayonnaise (all containing eggs) and a company called Hampton Creek, which has launched an eggless product called Just Mayo.

Unilever is accusing Hampton Creek of false advertising because Just Mayo contains no egg, so it 'can't be mayonnaise.' It is made from yellow pea shoots. Unilever claims the marketing of "Just Mayo" has "caused consumer deception and serious, irreparable harm to Unilever," and that calling the spread Just Mayo is "part of a larger campaign... by Hampton Creek to falsely promote Just Mayo spread as tasting better than, and being superior to, Best Foods and Hellmann's mayonnaise."

In the UK, food must be correctly labelled, and Just Mayo makes it clear it does not contain egg. As Just Mayo is a brand name, assuming that the labelling is clear, this will probably do. However, there is an obvious argument that calling a product that is not mayonnaise Just Mayo creates a misleading impression.

Does Hellmann's have a right to claim economic value in mayonnaise? Unlikely. There is legislation protecting the consumer from misleading labelling, which ensures anyone selling mayonnaise must label it accurately, and any company can trademark a brand and seek protection for it. It is unlikely Hellmann's could bring a claim in the English courts that Just Mayo's product amounts to unfair competition.

It remains to be seen who will be left with egg on their face.

Michael Hatchwell is immediate past president of Globalaw