To the unsuspecting eye, the delivery of everyday foodstuffs like cheese or chocolate spread to a nondescript trading estate would barely register - yet, the industrial-scale quantities of those goods which arrived in several former mill towns in northern England in just over a year contained a far more sinister ingredient - and they concealed what was later described as a "vast and complex criminal operation" with its roots in South America.

This week, 15 men were jailed over their roles in that operation - an international conspiracy to supply up to £1.4bn worth of cocaine between October 2022 and December 2023, which ended with one of the largest police forces in England and Wales securing its biggest ever bust.

The operation saw industrial units in Huddersfield, Cleckheaton and Halifax in West Yorkshire and in Blackburn, Lancashire, provide the perfect cover for seemingly ordinary shrink-wrapped pallets to be sorted.

As other perfectly legitimate businesses traded from neighbouring units, cocaine which had been ordered from South America would be cut out of blocks of gouda cheese and, later, other foodstuffs and re-packaged in cardboard boxes or black bin bags.

The drugs had been smuggled into the UK via Belgium, arriving in Dover as commercial freight and, from there, they were taken to a legitimate distribution hub in Derby before heading to the various industrial units, helping cloud the operation to any potential investigators.

Prosecutors would later say there were sometimes multiple pick-ups in a day at such sites, underlining the scale of the operation.

According to prosecutors, the payment for extracting the cocaine from two pallets was £3,000, with £1,000 paid for every extra pallet.

Aiden McCullagh, now 58, from Brighouse, who was tasked with unpacking the drugs then re-packaging them, was thought to have been paid £135,000 for his role.

Some of the blocks of cocaine retrieved by police were marked by so-called "cartel stamps" - brand logos which were intended as a signifier of quality to buyers.

Craig Goulding, now 39, from Wakefield, who was jailed in May for 25 years for his role in the operation, was also paid "thousands" to dispose of the waste food under the guise of his waste management business, police said.

Couriers from the Midlands, Lancashire and the North East would park up near the industrial estates, where their cars would be taken from them and driven to the units to be loaded with drugs.

Then, they would be taken back to the couriers for onward distribution across the north of England.

This process added another layer of security to the operation, so even those on the inside did not know the full details, according to police.

A West Yorkshire Police spokesperson said what sparked the start of their investigation was the seizure of cocaine and ecstasy worth £2m from a car that was stopped by officers in the East End Park area of Leeds in January 2023.

According to Det Insp Kevin Daly, from the force's Protective Services Crime team, officers working on what became known as Operation Grasmount "spent many months painstakingly building up a complete picture of how the operation worked and who were the key people running it in the UK".

"It was only by taking the required amount of time to gather a detailed and comprehensive evidential package that we were able to dismantle this distribution network as fully as we could and ensure that those who ran it were caught and held to account," Daly explained.

As the net was closing in, the group "changed tactics", according to the Crown Prosecution Service (CPS).

After a distribution hub in Lancashire was raided in May 2023, leading to the arrest and conviction of Saleem Chaudhri and courier Rieadul Mohabath, members of the gang instead started stashing the drugs in consignments of chocolate spread and frozen fish mince "due to their smell and density".

Meanwhile, motorway service stations were also used for some handovers.

In June 2023, a lorry driver from Belgium was arrested at Toddington Services, off the M1 in Bedfordshire, after he was seen meeting a courier and transferring boxes to his car.

Officers recovered 156kg of drugs from the lorry's trailer and 36kg from the car, with a total value of £19.2m.

Further arrests were made in December of that year, putting a stop to the conspiracy.

Those arrested and later convicted had a mixture of backgrounds.

Some were career criminals with multiple convictions, including for drug offences.

Others, like Harry Johnson, had no prior dealings with the police, but held a middle-management role within the group, organising deliveries, collections and payments.

Johnson, now 26, from Leicester, who had previously worked at a high street opticians, was living at home at the time and had enlisted his older brother Darren, now 31, into the conspiracy.

"It's a pretty serious, if not spectacular, entry into the criminal justice system," his barrister said.

The exact amount of drugs the gang distributed - and their value - is unknown.

However, a CPS spokesperson said available intelligence and evidential assessments estimated it to be between four and 14 tonnes, which equated to a street value of between £400m and £1.4bn.

Zoe Nixon, senior crown prosecutor for CPS Yorkshire and Humberside, said: "Behind the creative attempts of this group to conceal their dealings was an industrial-scale criminal enterprise which had been funnelling vast quantities of illegal drugs across the country.

"Each of the defendants had a role to play in keeping that enterprise operating, whether that was running the hubs, unpacking the drugs or transporting them to buyers across the country."

A further three men are still to be sentenced over their role in the operation, which a CPS spokesperson said involved other defendants already serving jail time.

"It's the biggest investigation West Yorkshire Police has ever had, without a doubt," said Daly.

"We seized over half a tonne of Class A drugs. This is not your everyday investigation."

Daly said every operation to get drugs off the streets was to be welcomed, with just under 60% of domestic violence offenders testing positive for drugs, while drugs also fuelled street violence.

"We are seeing it day to day with machete attacks," Daly said.

"By moving these drugs from the streets we are helping support victims of crime and ultimately reducing that threat across our communities."

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