Andrew Gurney, 51, of Middle Meadow Avenue in Quinton, Birmingham, was involved in a professional conspiracy to produce tons of amphetamine sulphate, a class B drug. The lab could produce up to £10 million-worth of drugs a month.
Gurney and Keith Davis - a 56-year-old of Brayfield Lane, Chalfont St Giles - were both jailed in June following a 12-day trial.
Gurney was sentenced to six years and three months imprisonment for conspiracy to produce a class B drug and possession of criminal property. He was known within the gang as ‘The Geek’ due to his specialist electrical installation and plumbing skills, and converted what had been a double garage outbuilding into the drugs lab.
Meanwhile, Davis was given a sentence of five years and three months for conspiracy to supply and produce a class B drug, and conspiracy to transfer criminal property.
But at a hearing on Wednesday, a judge at the Court of Appeal ruled their previous sentences were unduly lenient and increased them to 10 years.
National Crime Agency branch commander Matt McMillan said: “Keith Davis and Andrew Gurney were key players in running one of the largest drugs laboratories ever found in the UK.
“They carefully planned this criminal enterprise, undergoing chemistry training to run the facility, which was capable of producing 400 kilos of amphetamine per month, worth £2 million at wholesale and up to £10 million at street level.
“The drugs they produced were distributed to dealers from the West Midlands to London and Kent, and will have fuelled violence, fear and exploitation in communities across the UK.
“This ruling emphasises the seriousness of their criminality, and the NCA continues to target those behind the highest risk and most complex criminal threats to the UK.”
Speaking after the hearing, the newly appointed HM Solicitor General, Michael Tomlinson MP, said: “The illegal and dangerous drugs produced and supplied by both Davis and Gurney will have ruined lives, and so I am satisfied with the decision of the Court to order both offenders to serve longer prison terms.
“The new sentences are a better reflection of the seriousness of the crime of drug dealing and supplying at this level.”
Work started on the building in March 2020 and it began producing drugs in May of that year. The gang initially bought amphetamine pre-cursor chemical benzyl methyl ketone (BMK) but quickly realised it was more profitable to make it themselves.
The illicit drugs laboratory in Henley-in-Arden was discovered by National Crime Agency investigators after identifying encrypted messages on EncroChat, and raided the site in Ullenhall Lane in April, 2021, with assistance from Warwickshire Police.
Plumes of noxious fumes billowed from the outbuilding when it was opened by specialist crews from West Midlands Fire Service, who had to wait several hours before searching it due to the hazardous chemicals inside.
Waste products from the production process, which had been flushed into the sewerage system, had also contaminated a nearby field.
The gang members were all arrested on suspicion of drug offences at their home addresses on the same day.
The group's ringleader John Keet, 41, of Chalfont St Giles in Buckinghamshire, is due to be sentenced on October 28.