The gold, which weighs 104 kilograms (229 pounds), is on its way to Switzerland from the Cayman Islands when confiscated on June 1. No arrests were made, police said.
The British National Crime Agency (NCA) – a government law enforcement organization – reports that the gold is believed to be from Venezuela, from where it was transported to the Cayman Islands by private jet.
Border Forces agents at Heathrow Airport later moved to hold shipments when they arrived in England, based on intelligence provided by the NCA.
"We believe that this shipment is related to drug cartels operating in South America," Steve McIntyre, commander of the NCA Heathrow branch, said in a statement. "Working with partners abroad and in the UK, we can quickly identify and stop further movements.
"The business model of many organized crime groups depends on the ability to move money across borders, to fund further investment in criminal activities.
"If we can stop it not only causing disruption to the criminal network involved and preventing them from benefiting from crime, it will also stop the reinvestment."
Nick Jariwalla, director of Heathrow Border Force, added that removing large sums of money or gold from the control of criminal networks "hit them where they felt most, in their pockets."
"This is a major confiscation and shows how effectively the Border Force works with law enforcement partners, both at home and abroad, to fight organized crime," he said.
Lynne Owens, NCA director general, praised the work of the two teams and said that it represented "further progress" in the struggle to stop Britain being used as a "route for illicit finance."
"Extraordinary work by our international network and others supported by Border Force," he wrote on Twitter.
While gold was confiscated last month, a recent trial at the Uxbridge Magistrates Court in London allowed it to be officially held under the Proceed of Crime Act.
Gold will now be part of an international money laundering investigation led by the Cayman authorities, with support from the NCA.
NCA and Border Forces Heathrow has previously found large numbers in relation to international drug trafficking from South America.
In 2017, a Heathrow security worker was accused of trying to import up to £ 480,000 ($ 600,120) of cocaine to Britain from South America.
The worker was on sick leave when he traveled to the airport wearing his uniform and met a Colombian drug courier at the airport toilet, where he was later arrested by police, the NCA said.
He was later sentenced to 13 years in prison.