On January 17, as Novak Djokovic battled Fernando Verdasco on Rod Laver Arena, two men in their late 30s, travelling on Estonian passports, were pulled aside by Australian Border Force officials at Melbourne Airport's bustling international arrivals terminal.
The men had previously travelled to countries hosting major sporting events, including those on the International Tennis Federation circuit. For travellers who had marked the purpose of their visit as tourism on their entry documents, they were carrying some peculiar items.
Investigators discovered several microchip processors the size of a human hand, several remote car-unlocking devices, small bundles of wire, a soldering iron and glue. The two Estonians appeared nervous, as if they knew they had some serious explaining to do. And they did.
In a drab interview room, one of them told investigators he had been dispatched to the Australian Open to run a "court-siding" operation. The practice is banned by tennis authorities and involves the murky but not necessarily illegal activity of relaying point-by-point information via hidden equipment.
That equipment is often strapped to a court-sider's leg. The information is sent to gamblers betting on the in-play market, where they can win huge amounts of money on the outcome of a single point.
The scam involves taking advantage of the slight delay in broadcasting a live tennis match to bookmakers, effectively allowing the gambler to know the outcome of the point they are betting on.
The two men are suspected to have links to Eastern European organised crime syndicates, and after the Victoria Police's sports integrity unity and Tennis Australia integrity investigators were notified, they were denied entry into Australia. The pair never left the airport.
Detectives are now scouring through the data downloaded from the men's phones to answer several unknown questions, including who the men were working for and how many international sporting events they have previously attended.
"These guys were highly professional," says an official. "It's almost certain they were working for a syndicate following the [tennis] circuit."
Australian Border Force commissioner Roman Quaedvlieg told Fairfax Media: "We know that criminal entities, especially those from Eastern European countries and associated crime syndicates, target international sporting events to undertake corrupt betting practices."
The airport operation is a reminder of the threat posed by gambling to sport. Not that it is needed in the tennis world. Three days before the Australian Open began on January 8, it was reported that the reigning Australian Open boys champion, Oliver Anderson, had been charged by Victoria Police with match fixing offences in relation to a tournament in Traralgon last October.
It is understood Anderson was approached to drop the opening set of his first-round match at the tournament.
Police are now investigating under whose directions Anderson was allegedly acting. On January 11, the Tennis Integrity Unit announced the outcome of a 2013 corruption probe that ensnared several Australian tennis players.
Nick Lindahl, who retired after the scandal first broke and has been convicted in a criminal prosecution, was banned for seven years for match fixing at a tournament in Toowoomba in 2013. Another player, Brandon Walkin, was also found to have committed corruption offences.
"Court-siding" is considered less serious than match-fixing as it involves no contact with players. The Victoria Police failed in a previous effort to prosecute a 2014 Australian Open court-sider for feeding information to an international betting agency based in London, as it wasn't clear sports cheating laws applied to the activity.
But the activity clearly involves the defrauding of honest betting-exchange gamblers or bookmakers on the other side of a court-sider's betting. And anti-corruption investigators say a syndicate prepared to engage in court-siding may also engage in match-fixing.
Police privately say that while Tennis Australia has improved its anti-corruption measures, the sport itself remains one of the most exposed to corruption and some overseas tennis federations are woefully ill-prepared to deal with the problem.