A total of nine arrests were made in the operation, including two men the Guardia Civil described as expert pilots. As well as the helicopter containing drugs, a French-made Alouette III, a similar aircraft was also seized in a nearby location.

Among those arrested are believed to be mechanics who maintain the helicopters using parts brought in from former Soviet Union countries.

The gang’s smuggling route involved flying across the Strait to northern Morocco, where the drugs were loaded.

The pilots would then return to Spain at night, travelling at a height of no more than 30 metres above sea level without using the helicopter’s lights and with navigation systems turned off to avoid electronic detection.

According to investigators, a helicopter such as the one Mr Blaha was piloting that night is “virtually undetectable because it flies so low that the mountains cause the waves received by Spanish radars to be lost”.

“Those on board during these flights are taking a great risk,” the investigators added.

The fee charged by a pilot such as Mr Blaha is believed to be around €150,000 per flight.