The drugs, valued at £90m, were seized when Dutch authorities swooped on two vessels off the coast of Holland.

Twelve people are being questioned. Ten of them were detained on the two vessels. A further two, one in Holland and another in Sussex, were arrested by Dutch and British authorities.

The two boats had been under lengthy surveillance as they sailed from north Africa, taking a long detour round the coast of Scotland before heading across the North Sea to the Netherlands.

Officers from the National Investigation Service (NIS), a branch of Customs and Excise, passed surveillance details to Dutch authorities while two vessels carrying the cannabis passed through British waters.

Customs and Exise Investigator Ranald Macdonald on the combined operation

Customs vessels monitored the boats, named Canute, and Onderneming as they made their way through the Pentland Firth sea between Orkney and the north coast of Scotland earlier this week.

British customs officials then pulled out of the operation when it became clear that the vessels were headed for Holland and into the jurisdiction of the Dutch authorities.

An NIS spokesman said: that although the haul was bound for Holland, some of the drugs could have been transported back to the UK.