UK authorities found 1.2 tons of cocaine on a luxury yacht at the port of Southampton, in the country's largest ever seizure of a Class A drug.
The drugs were found in June, but the seizure was only made public on Wednesday after several arrests were made in the Netherlands.
The yacht had been due to arrive in the Netherlands with its cargo. (See video below).
Authorities had been tracking the vessel since May, after suspicions were raised by French authorities while the boat was in the Caribbean. The drugs are believed to have originated in South America, and to have been packed and loaded onto the vessel in Venezuela.
A Dutch official said that about 40 percent of all cocaine brought into Europe is trafficked using smuggling routes from the Caribbean.
UK said that the cocaine, which was 90 percent pure, would have been cut with other substances to produce eight tons for sale on the street, with a value of £300 million ($490 million).
Six Dutch nationals, including the owner of the boat and his three sons, were arrested in connection with the seizure.