A hat, some photographs and a notepad donated by one of the world's most celebrated chefs provide the only clues to a great culinary mystery.

Those items were all left at the table by a motorcycle courier from Switzerland when he disappeared in the middle of an international eating marathon.

Pascal Henry, 46, began his quest to eat at all 68 three-star Michelin-rated restaurants in 68 days — a 24,850-mile (40,000km) journey that would take him through nine countries — last May.

But in June he disappeared from a table at El Bulli, the celebrated Spanish establishment, without paying and has not been heard of since. Spanish detectives said yesterday that they had begun an investigation into the disappearance after receiving a request from their Swiss counterparts through Interpol.

Detectives in Geneva were alerted by Mr Henry's relatives when he failed to show up for work on July 15 after what was supposed to be one of the greatest culinary adventures of modern times.

Mr Henry had finished his dessert at El Bulli — restaurant No 40 — when he got chatting to a couple at the next table, according to a Spanish police source.

He offered them his visiting card, but when he looked in his pockets he found he had none on him. So he popped out to his car to get one - and that was the last that was seen of him.

Left on the table were some of Mr Henry's photos, his hat and a notebook given to him by Paul Bocuse, the celebrated French chef, on the first leg of his journey.

Mr Bocuse had noted the dishes that Mr Henry had eaten in the book and told him to get the other chefs on the list to do likewise.

The French cook also faxed all the 67 remaining restaurants that Mr Henry was due to visit and asked them to treat him with particular attention.

“I decided to help him,” Mr Bocuse said. “I wanted him to receive the same warmth everywhere. It's not easy to go from one gastronomic table to another alone and without someone to share your enthusiasm.”

The enigma has sparked intense speculation in Switzerland, where it has been suggested that Mr Henry slipped away because he ran out of money. Mr Henry's relatives dismissed these claims.

A meal in El Bulli, which is owned by Ferran Adrià - widely considered to be the world's finest chef — costs about 165 euros (£130) without wine. Dishes include turtle dove with blackberry caviar, caramelised trout roe and white garlic soup.

Mr Henry's family said that although the courier had a relatively small income, he had spent months planning the trip and years saving for it, to satisfy his love of fine food.

Philippe Rochat, chef at the Hôtel-de-Ville restaurant in Crissier in Switzerland — which was Mr Henry's second stop — confirmed his passion.

“I've rarely seen someone with such knowledge,” he said. “He came into the kitchen for a discussion with the team.”

The mystery surrounding the Genevan gastronome has been fuelled by reports that he is divorced and deeply secretive and went missing for several months as a teenager.

One theory is that he could have fallen from the cliffs by El Bulli. But this was dismissed by Juli Soler, the restaurant manager.

“The terrace was packed. Someone would have seen or heard.”

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