The whale is around two years old and 7 or 8 metres long. However, biologists are concerned about his rapid weight loss as he cannot find the invertebrates that are his normal food source in the depths of the Pacific.

“We are very worried about his future, as his fat, which is his fuel to travel, has gone down a lot. He is exhausted and just skin over bones. We have not seen him eat since we started tracking him,” Hansen told Reuters.

Wally entered the Mediterranean through the Straits of Gibraltar and followed the Moroccan coast before cutting across to Italian shores and then heading for France.

Travelling 80 to 90 kilometres a day, he was spotted very close to the shore of Antibes and was approaching the Spanish coast.

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“It is trying to enter harbours, as if to find a way out. Its strategy should work and we hope it can make its way back to Gibraltar in about a week,” said Hansen.

However, escape may not be so simple. A few days ago, Wally got caught in a fishing net off the Camargue coast but managed to free himself. There are concerns he may get confused by heavy shipping traffic in the Gibraltar Strait.

The Telegraph, London