A record £300 million haul of cocaine has been seized and six alleged members of an international drugs gang arrested, officials said today.
A total of 1.2 tonnes of cocaine, with a purity of 90%, was found hidden inside a 65ft pleasure cruiser at Southampton docks in June.
It is the biggest haul of Class A drugs ever found in the UK, officials from the UK Border Agency (UKBA) and the Serious Organised Crime Agency (Soca) said.
French authorities were alerted to the suspicious £1 million craft Louise while it was in the Caribbean in May and it was then tracked to Southampton, on its way to Holland.
Officials spent six days searching the vessel and found the drugs packed in a specially-designed compartment beneath the boat's bathing platform.
It is understood the cocaine, which originated in South America, was packed inside the boat while it was in Venezuela.
The drug was 90% pure, while the average purity of cocaine seized at the UK border is just 63%, officials said.
The haul is estimated to be worth between £50 million wholesale and £300 million on the streets.
Since the drugs were found in June, the UKBA has helped Dutch police track members of the gang and six men were arrested during early-morning raids yesterday - two 44-year-olds in Amsterdam, a 60-year-old in Meppel, two, aged 32 and 34, in Heusden, and a 27-year-old in Waalwijk.
A total of 100,000 euros (£87,300), two Harley Davidson motorcycles, two firearms, a silencer and some ecstasy were also seized.
Immigration Minister Damian Green said: "This was a significant drugs seizure which was made possible by the co-operation of our international partners.
"UK Border Agency staff have shown vigilance, dedication and determination to uncover this shipment.
"Our efforts have helped bring an international crime gang to book and the message is clear: we will investigate and prosecute anyone who tries to smuggle banned substances through UK borders.
"By keeping the border secure we play a key role in stopping drugs entering the UK and in reducing the harm they do to our communities.
"We aim to protect society from the violence and corruption that always accompanied the trade in illegal goods."
The Dutch police were acting on intelligence provided by Soca's international network and the French Customs Investigation Service (DNRED).
Brodie Clark, head of the UKBA's border force, said: "This has been an enormous seizure of cocaine. This is the largest we have on record.
"It's a major seizure. It's about serious crime, it's about major criminal disruption."
The international co-operation was a "strong and powerful example of more to come", he said.
Asked about how the drugs were hidden, he added: "It was ingenious, it was difficult to find. Skilful people spent a number of days looking for it."
David Armond, deputy director of international operations for Soca, said the Louise had been "of interest for some time".
Operation Parsons showed the trust between international partners as the £1 million vessel was "destroyed to find the load", he said.
He said the high purity of the cocaine meant it would make about eight tonnes of saleable drugs once cut.
This was the equivalent of seven million street deals - "equal to about one third of the requirement for the UK market over the course of a year", he said.
"It's unusual for a load like that to get to the shores of the UK.
"It is undoubtedly the case that, had this vessel been allowed to get to its destination, a significant amount of this load would have been transported back to the UK."
Jim Jarvie, deputy director for the UKBA's crime directorate, said the drugs were destined for Holland, from where they would have been distributed across Europe.
Commissioner Gert Ras, of the Dutch National Crime Squad, said all six arrested men were Dutch nationals.
They included the 60-year-old owner of the boat and his three sons, aged 27, 32 and 34.
A further arrest of a seventh Dutch national is also expected, he said.