The operation was carried out by the joint National Crime Agency (NCA) and Metropolitan Police Organised Crime Partnership (OCP).
The extensive criminal organisation supplied class A drugs and laundered millions of pounds in illicit profits.
They deposited their cash into front company bank accounts, before transferring it to a destination account in Dubai.
The organisation was led by Baljinder Kang, from Tilbury, and his right-hand man Sukhjinder Pooney, from Gravesend.
They used encrypted smartphones as well as a succession of unregistered “burner” phones to direct the group’s activity.
Officers seized more than £1.4m in cash, with at least £1.8m more known to have been laundered by the criminal network.
More than 37kg of class A drugs were seized, including heroin and cocaine with a street level value of over £3.5m, a handgun with ammunition, and 50kg of ketamine.
Several drug deals were noted in files found by officers searching Kang’s home after he was first arrested in January 2018.
Despite having very little legitimate income, Kang lived a lavish lifestyle, the NCA said.
He purchased luxury goods from designer stores including Gucci, Ralph Lauren and Harrods and owned watches worth £12,000 and £36,000.
He also leased a Mercedes and an Audi A3, and travelled regularly to the United Arab Emirates.
Pooney was found guilty yesterday of conspiracy to supply class A drugs having previously pleaded guilty to money laundering offences.
Kang pleaded guilty to all charges against him on 23 May.
Detective Superintendent Simon Moring from MPS Central Specialist Crime, said: “This was a lengthy and thorough operation involving extensive joint work between a dedicated team of Met and NCA staff – all of who are committed to dismantling organised criminal gangs.
“I hope that today’s result is a stark reminder to those involved in organised criminal activity that the Organised Crime Partnership is far reaching and will use all powers available to us to secure a conviction.”
Sentencing is scheduled for 24 July at Kingston Crown Court.