Jake Levene, 22 (right) and Mandy Lowther, 21, who ran a dark web business selling the potentially lethal drug fentanyl to customers across the world. Photo: NCA/PA

Three men including an ex-university student who used the 'dark web' to sell a powerful drug linked to 125 deaths in the UK have been jailed for a total of more than 40 years.

Jake Levene, 23, Lee Childs, 45, and Mandy Lowther, 22, set up a business titled 'UKBargins' importing and exporting fentanyl and one of its analogues, carfentanyl.

The class A drug, which is prescribed for severe pain relief, can be fatal in doses as small as 0.002g, a court heard.

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Photo issued by the National Crime Agency (NCA) of items in a workshop used by, Jake Levene, 22, Lee Childs, 45 and Mandy Lowther, 21, to make the potentially lethal drug fentanyl and who ran a dark web business selling the drug to customers across the world. Photo: NCA/PA

The brazen trio operated their business from a rented industrial unit under a fake name where they mixed the drugs with bulking agents and packaged them for posting.

"Highly intelligent" Levene jointly controlled the premises in Leeds, West Yorks., along with amateur boxer Lowther while Childs was responsible for posting packages of drugs to customers.

The drugs were posted to customers throughout the UK as well as the US, Germany, Norway, Canada, Australia, Argentina, Canada, France, Singapore, Holland and Spain.

But the organised crime gang were apprehended two months later in April 2017 following a police raid in what is believed to be the largest single seizure of the drugs in Europe.

Officers discovered at least 635g of pure carfentanyl - which is generally used to anaesthetise elephants and polar bears and thought to be 3,000-5,000 times stronger than heroin.

An exact measurement of the quantity could not be provided as forensic scientists thought the drug was too dangerous to handle.

Police also found a quarter of a kilogram of fentanyl which is believed to be 50 times stronger than heroin.

A recovered laptop belonging to Levene, who was an A* student at school, also showed 2,853 sales to 443 customers worldwide, with 172 in the UK for a total of Â£163,474.

The trio pleaded guilty to two counts of conspiracy to evade the prohibition on the exportation of a controlled Class A drug and two counts of conspiracy to supply a controlled drug of class A.

Levene, who previously started a university degree in aero-engineering at Sheffield University, and Lowther were each given a 16-and-a-half-year sentence.

Co-accused Childs was handed a sentence of 10-and-a-half-years at Leeds Crown Court.

Prosecuting, Paul Mitchell QC said: "These three defendants were using the Dark Web to sell Carfentanyl and Fentanyl to customers abroad.

"They had exported or supplied at least 2,853 packages to at least 443 customers. They had received an income of Â£163,474 in cryptocurrency.

"They were making significant money it's plain from what was going on. The money seems to have disseminated rather than to build up their assets.

"Levene and Lowther were jointly responsible for a very sophisticated operation. It was set up as a business and run as a commercial business."

Post-mortem results indicate that 125 drug-related deaths in the UK are known to be linked to fentanyl or one of its analogues, including carfentanyl.

The majority of these deaths occurred before mid-2017, though cases have continued into 2018.

Carfentanyl is generally used to anaesthetise large animals such as elephants and polar bears.

The court heard that Lowther almost died after being exposed to the drugs he was sellings.

He was admitted unconscious to Leeds General Infirmary on February 20, 2017, and transferred to the intensive care unit.

He was in a coma and was found to have a hypoxic brain injury. His illness was linked to exposure to fentanyl and carfentanyl.

Lowther later recovered and was discharged on March 2, 2017, but despite his near-death experience continued to supply the deadly drugs until the unit was raided.

Officers discovered the trio had turned over Â£163,474 during the indictment period between December 1, 2016, and April 30, 2017.

The men were arrested in April 2017 after National Crime Agency officers and West Midlands Police raided the unit.

Defending Levene, Michael Gomulka said: "He has been diagnosed with having Asperger's Syndrome.

"Asperger's brings with this disassociation between one's self and the outside world.

"This is not a hardened criminal.

"He saw it as a challenge. It's numbers on a screen without thinking of the human cost.

"This is not someone you would expect to find as a leading role in a Class A drug dealing enterprise."

Defending Childs, who has 10 previous convictions, Stuart Field said the defendant is a married father-of-two and previously worked as a roofer.

He started to self-medicate because of health problems and then began using heroin.

Sentencing the trio, Judge Mushtaq Khokhar said: "When it comes to Class A drugs the courts are very familar with heroin, crack, crack cocaine and so forth."We see that everyday of the week in these courts so anyone who is involved in distribution of drugs can expect higher sentences.

"It's not just those who are addicted to drugs who suffer misery but also society at large.

"This was a sophisticated operation, small I accept but nevertheless sophisticated.

"One only has to look what the officers found when they raided the unit. There were specific areas set aside for specific tasks to be performed.