The money would be laundered through the Pyrmont casino by a professional gambler in order to minimise the risk of not just losing it, but of arousing suspicions of the authorities.

The gambler would allegedly be paid out in the form of a casino cheque which would then be taken to the gaming capital of the world, Las Vegas, where it would be cashed in and the alleged dirty drug money laundered.

The alleged plan, revealed by NSW police on Friday, came unstuck when police were called to Sydney's Hilton Hotel after an anonymous tip-off that the occupant of room 3026 had a gun.

The occupant –  Sydney-based former cage-fighter and racehorse trainer-turned personal trainer Sean Carolan – didn't have the gun, only the bag of cash.

It was the discovery of that bag of cash, in August 2011, that put police, the Australian Crime Commission, the NSW Crime Commission and the FBI in the US on the trail of an alleged criminal network that had already laundered at least $5 million, mostly through The Star casino.

And it was that investigation that culminated on Thursday night with the arrest of high-profile music promoter Andrew McManus, 54, as he landed in Melbourne on a flight from New Zealand airport, following the arrests in Sydney of crime figure Craig Haeusler, Kings Cross solicitor Michael Croke and Auburn pastry shop owner Zeki Atilgan.

Mr Carolan's business partner, US businessman Owen Hanson jnr was arrested by the FBI as he played golf in San Diego. Mr Carolan has not been arrested or charged with any offence.

Mr McManus, Mr Haeusler and Mr Croke have been charged with perverting the course of justice, intention to defraud by providing a false or misleading statement and knowingly participating in a criminal group.

The charges allegedly relate to statements made during a NSW Supreme Court case by Mr Carolan to recover the money.

Mr Atilgan was charged with two counts of money laundering. Mr Hanson was charged by the FBI with money laundering and drug offences

Head of the NSW Police's Organised Crime Squad, Detective Superintendent Scott Cook said it will be alleged that those charged had various roles within the alleged criminal network.

"We find with criminal groups that individuals play key roles and significant roles, they don't all undertake the same roles," Superintendent Cook said.

"Whilst a person is charged with a criminal group offence that's not to say that person was importing drugs personally, if that was the case they would have been charged with that."

On the night police seized the suitcase of cash, Mr Carolan said he was merely minding the money for Mr Hanson, his business partner, who didn't want to lose any more at the casino.

CCTV footage from The Star obtained by the police shows that, earlier in the day, Mr Carolan and Mr Hanson were in a heated conversation with Robert Cipriani, a well-known American high roller who calls himself Robin Hood 702 (702 is the telephone code for Las Vegas).

Police records note that Mr Cipriani "is well known to the casino and is currently of interest to the Australian Federal Police".

The day after the cash was seized, Mr Cipriani left for Los Angeles.

The money was confiscated, but Mr Carolan took action in the NSW Supreme Court to have it returned.