It was a Wednesday morning in Rome when Italian police received a pivotal Interpol red notice from Victorian police.

By about 4pm the next day, Perry Kouroumblis would be under arrest for the killings of two Australian women almost 50 years ago.

Finally, it seemed, we could be closer to understanding how Suzanne Armstrong and Susan Bartlett were brutally murdered in their Easey Street home in January 1977.

The women in their 20s were found dead with multiple stab wounds in their Collingwood share house. Ms Armstrong's 16-month-old son found was alone in his cot in the aftermath.

But this month's breakthrough arrest was only able to take place because Mr Kouroumblis, 65, had travelled from Athens to Italy, with Italian authorities telling the ABC his reason for travel was "tourism".

He had been living in Greece, where laws around the serving of international warrants had prevented Australian police from ordering his arrest.

How Italian police pounced on Kouroumblis in Rome

Italian authorities had to do some careful work to intercept the alleged murderer.

Speaking exclusively with the ABC, the head of the police unit at Rome's Fiumicino Airport, Chief Commissioner Fernando Speziali, said when the alert was received from Australian police, Italian Interpol had to monitor flights coming in from Greece.

Sure enough, Mr Kouroumblis was detected on SKY Express flight GQ 820, destined to arrive on Thursday, September 19, around midday.

"This office took the necessary measures to stop him because, as the flight was within the Schengen area, he wouldn't be subject to border controls," Commissioner Speziali said.

The Schengen area is a group of 29 European countries, including Italy and Greece, that allow citizens to travel cross borders freely.

Additionally, Australian police knew Mr Kouroumblis by another first name – the anglicised 'Perry'.

But according to Commissioner Speziali, he was travelling on a Greek ID by the name, Perikilis Kouroumblis.

Commissioner Speziali said once Mr Kouroumblis came off the flight, he was stopped in the Schengen arrivals area of the airport and led into police offices where they obtained his fingerprints.

"After having verified that he was the wanted subject, we arrested and took him to Regina Coeli Prison in Rome," he said.

The prison is where Mr Kouroumblis currently remains.

Now that Mr Kouroumblis has agreed to his extradition, the Italian Justice Minister has 45 days to proceed with it.

Through his Italian lawyer, Mr Kouroumblis also maintained his innocence.

Arrest makes international news

News of the arrest broke in Australia two days later, with Victoria Police's Chief Commissioner Shane Patton making the announcement to a press pack in Docklands.

One journalist was so overcome by the news, she clapped as the press conference ended.

Back in Italy, the story hit the newspapers.

In Il Messagero, the headline read "The Monster of Melbourne caught in Rome, 47 years later".

The headline in Il Tempo was: "Australian Cold case closed at Fiumicino".

In the Corriere della Sera: "After 47 years, the killer of Melbourne caught".

The article reports that Mr Kouroumblis was wanted on an international level for seven years, although Australian police wouldn't confirm exactly how long they'd been waiting to make the arrest.

Despite the certainty in Italian reporting, it's important to note Mr Kouroumblis has not been found guilty of the crimes or been tried in court over the matter.

Mr Kouroumblis will be charged with two counts of murder and one of rape when he reaches Victoria.

Commissioner Speziali said he felt "satisfied" his team was able to play a part in the arrest, "albeit in a small way".

He said cold case investigations took "perseverance" and "skill" and could provide much needed answers for surviving family members.

"This is a fundamental point for every policeman in any country. This is why I feel connected to my Australian colleagues," he said.