Experts have discovered the cause of death for a sperm whale that washed up unexpectedly on the shores of Spain’s La Palma island - €500,000 of “floating gold”.

The impressive discovery was made after experts from the University of Las Palmas de Gran Canaria carried out a post-mortem, with authorities initially unsure how the 15-ton, 13-metre-long whale washed up on Nogales beach last month.

“When I dissected and removed the stone I turned around and everyone on the beach looked at me in surprise, but for me at that moment I understood where the origin of the infection was coming from,” Antonio Fernández Rodríguez, the head of the Institute of Animal Health and Food Security at the university, said.

The stone, he explained, was a large lump of precious ambergris, a rare substance sometimes known as “floating gold”.

Highly prized by perfumers, the 9.5 kg lump found in the whale can sell for up to €500,000 (£430,000).