Three men jailed for trying to smuggle nearly 40kg of methamphetamine into the country from Mexico refused to give up the identities of their puppet masters.
But police believe an organised criminal gang was pulling the strings, and may have later relied on a crooked cop to leak classified intelligence about the covert operation.
On November 1, 2017, a huge cache of drugs was intercepted at Christchurch International Airport after the arrival of a Singapore Airlines flight from the United States.
It had arrived from Mexico and was hidden in a shipment of safety lights.
But inside the 20 boxes was up to 1.2kg of 80 per cent pure meth - nearly 40kg, the High Court at Christchurch heard on Wednesday.
It was the South Island's biggest ever meth bust and worth at least $24 million, while police believed the drugs - if sold in gram amounts - could be worth up to $50m on the street.
Police and Customs then executed Operation Grandeur, which saw several properties in Christchurch and Auckland raided after a covert two-week sting.
Arrested in the searches were Jonathan Seal, 27, Michael Harrison Cooper, 33, and Auckland freight worker Simote Vea, 38.
But none of the trio identified anyone "further up the food chain", the court heard, while nearly a year later a constable began making suspicious inquiries about Operation Grandeur in the police's national intelligence application system (NIA).
During his four police and Customs interviews, Vea said he was in contact with a person known only as "Andy".
Vili Taukolo, a now disgraced and jailed former South Auckland police officer, first searched the Māngere address of one of the men - believed to be Vea.
Vea was an Auckland customs brokerage manager for a freight firm, earning $145,000 a year.
After finding the Māngere man, Taukolo then made several queries about Seal and Cooper.
Both Canterbury men liked living the high life.
They were friends, known in the Christchurch party, gym and bar scene, with Cooper once a competitive bodybuilder who held a Canterbury title.
Taukolo, meanwhile, also sought out details about the progress of Operation Grandeur in October 2018.
He also dug out information in the NIA which had been provided in confidence to Crimestoppers.
The 31-year-old viewed "a large number" of documents linked to the investigation, court papers obtained by the Herald show, and printed 17 classified documents about the drug bust.
After irregularities in Taukolo's use of the NIA led to an audit, police raided the home of one of their own in March this year.
They found $30,000 of bundled cash in a bedroom drawer, while under his mattress were several NIA documents.
Police analysis of Taukolo's bank accounts later revealed cash deposits of more than $12,000 during January and February this year, court documents read.
He was a mole, an informant inside the New Zealand Police leaking information to those in the criminal underworld.
The Herald asked police who, or which gang, Taukolo was acting for and leaking intel to.
"We know through our investigation that Mr Taukolo provided some information to third parties, however, we won't be commenting further on specifics in relation to other individuals," a police spokesperson replied.
In all, Taukolo had been paid about $70,000 by crooks for his leaks, court papers show.
He is now serving a prison stint of two years and two months after being sentenced earlier this month in the Auckland District Court.
• Trio get lengthy jail sentences for South Island's biggest-ever meth bust
• Revealed: Corrupt Auckland cop Vili Taukolo printed classified intel about $50m Mexican drug deal
• Corrupt Auckland cop revealed as informant for criminal underworld within NZ Police
• Mates, meth and millions: Kiwi duo face jail for $50m drug import
This week, Seal, Cooper and Vea were all handed hefty jail sentences for their roles in the scheme.
The court heard Seal and Cooper gave vague and unverifiable stories about how they got entangled in the drugs bust.
Their lawyers said the Christchurch pair were naïve young men who had supposedly met a man in a bar who proposed a business venture – something about building a new carpark.
They communicated with burner phones, while importation documents were signed, duty and GST payments were made, and Seal chased up a freight company.
After police and Customs officers uncovered the meth package, they replaced most of the drugs with a substitute substance before delivering the consignment.
But undercover officers were watching.
When police raided Cooper's home they caught him trying to flush the product in his bathroom, the court heard.
Both Cooper and Seal admitted a charge of importing methamphetamine, while Vea went to trial and was found guilty by a jury earlier this year of importing meth on three occasions in November 2017.
Vea, a father of four, was sentenced to 15 years and seven months' imprisonment with a minimum non-parole period of seven-and-a-half years.
Vea's crimes also included two shipments from Canada where the drugs were tucked away in LED panels and karaoke electronics.
Seal and Cooper were each jailed for 12 years and four months, with no minimum non-parole periods.