The operation, carried out in conjunction with Britain’s National Crime Agency, saw Spanish customs agents boarding the boat in the Bay of Cadiz where it had sought shelter from a storm, a police statement said.

The vessel, which had been under police surveillance following a tip-off by the British authorities, had previously been docked at Cadiz marina, which lies on the Atlantic coast of southern Spain.

“Investigations had discovered the boat was going to be used to load a large quantity of hashish in Morocco that was to be transported to Latin America,” police said.

The boat had set sail for the western coast of Morocco where it picked up its cargo, but was then forced back towards Spain due to bad weather in the Strait of Gibraltar, where it was “surprised” by a customs patrol vessel.

Agents boarded the boat and found “numerous packages made of burlap and raffia, which are often used to transport these types of drugs,” counting a total of 130 packages containing some 4,400 kilograms of hashish.

The boat was taken to Cadiz and its two British crew members were arrested, it said, without ruling out further arrests.