Two Dutch members of an international organised crime group have been given long prison sentences after an investigation by the British National Crime Agency into Britain’s biggest ever detected drugs smuggling operation.

The offenders are thought to have smuggled up to £7 billion worth of heroin, cocaine and cannabis to Britain between 2016 and 2018 alone, the agency said.

Among the 18 defendants, 54-year-old Johannes Vesters and 53-year-old Barbara Rijnbout, both from Utrecht, were given 20 and 18 years in jail respectively.

A 35-year-old man from Amsterdam was given a two-year sentence, six months suspended while the 24-year-old son of Rijnbout was given a two-year suspended sentence.

A warehouse in Uithoorn was among a network of places used to store the drugs.

Most of the gang members are British nationals. Gang kingpin, 59-year-old Paul Green, was sentenced to 32 years in jail following the 23-month trial, the longest-running in Britain, police said.

“To avoid detection, the gang concealed its drugs in consignments of strong-smelling foodstuffs such as onions, garlic and ginger. The crime group bought so many onions – between 40 tonnes and 50 tonnes a week, that it couldn’t get rid of them and often sent them back to the continent to act as another cover load,” police said.

Dutch police became involved in 2016 when an innocent Dutch truck driver became suspicious of a consignment and called the police, who found eight bricks of cocaine. From then on gang members were kept under surveillance and phone calls tapped.

The international cooperation between the two police forces led to the seizure of 450 kilos of cocaine and heroin and two tonnes of cannabis across three seizures at the ports of Killingholme and Immingham, both Lincolnshire, and one in the Netherlands.