A gang leader and his son who used a luxury yacht to smuggle cocaine with a street value of £300m into the UK from Venezuela have been jailed.

 The pair, from the Netherlands, hid a tonne of cocaine in a deep compartment specially designed for smuggling. The haul - one of the UK's biggest drugs seizures - was located by border officers in Southampton last year. The men were jailed along with a third man, but the gang leader's other son was acquitted after a trial. Defendants referred to in court only as Klaas L, Robert L and Mohamed Z were convicted of being involved in the transportation of cocaine. Wire tap Their co-accused, Arjan L, 35, was acquitted of the same charge. Klaas L, 61, owner of the yacht, was jailed for seven years; Mohamed Z, 45, for eight years; and Robert L, 33, who was also convicted of possession of a firearm, for five years following a trial in Rotterdam. The drugs were so well hidden that it took the border force, who had been tipped off, six days to find them. The 90% pure drugs were so well hidden it took six days to find them Had the gang been successful, the cocaine could have been transformed into about seven million street deals - a third of the annual UK market, the border force confirmed. Authorities intercepted gang members' telephone conversations with a wire tap and tracked the £1m 65ft pleasure cruiser, the Louise, as it travelled on board a container ship from the Caribbean to the UK. Border force officers discovered a tonne of 90% pure cocaine, the court heard. The haul accounted for almost half of the total cocaine seizures across the UK in 2010/11 which was 2.4 tonnes. Border force director general Brian Moore said: "Today's conviction and sentences see a serious international drug smuggling crime gang brought to justice and clearly demonstrate how the border force are playing a lead role in the fight against the global trade in illegal drugs, helping to protect our communities here in the UK." Loaded machine-gun When the smugglers were arrested in a series of police raids across the Netherlands, officers recovered a loaded machine-gun, a second firearm with silencer, 1.5m euros (£1.2m), and two Harley Davidson motorcycles, the border force said. The cocaine, destined for the Netherlands, via England, was packed inside the boat while it was in Venezuela. The haul is estimated by the border force to be worth about £50m wholesale and up to £300m on the streets. In a police statement, read to the court, Robert L, 33, told how he and his father took the drugs onboard the boat at Isla Margarita, Venezuela. He claimed his father and Mohamed Z made all the decisions and confirmed the final destination for the cocaine was to be Waalwijk, just north of Eindhoven, where the drugs would be bulked out. Klaas L, from the northeast of the Netherlands, was also convicted of laundering 60,000 euros (£48,000). Mohamed Z, from Amsterdam, was also convicted of laundering almost 1.5m euros but was acquitted of possession of a loaded firearm. Passing sentence, the judge said: "The international trade in hard drugs is highly profitable and, with this trade, large criminal profits are gained. "The suspects' actions were mainly financially driven and they did not worry about the social consequences." The yacht has been confiscated and will now be used as a training tool for specialist Border Force search officers.