Hazel Behan, 37, believes her attacker may have been Christian B, the main suspect in the disappearance of Madeleine McCann.
He was convicted of a similar rape a year after Ms Behan’s assault and two years before Madeleine’s disappearance.
This week, detectives collected their own archived files from the Portimao court to see if they could build a case against the suspect.
One problem they will face is that vital forensic evidence with DNA potential has been destroyed by order of a judge, a common practice in Portuguese cases where no suspect is identified.
A source told Sky News: “Detectives are looking again for new evidence and the investigation is reopened. ”
Ms Behan was a 20-year-old party representative who arrived in Praia da Rocha on the Algarve coast in April 2004.
Two months later, a masked man climbed onto her apartment balcony and attacked her while she was sleeping in the early hours of the morning.
He held a knife to her throat, tied her up and gagged her, then raped her repeatedly.
During the attack, he threatened to kill her and let her bleed before fleeing through the balcony.
Last month, when German vagrant Christian B was named a prime suspect in the Madeleine case – and Ms Behan read her conviction for raping an American in surprisingly similar circumstances – she contacted the Scotland Yard Madeleine team .
She told the Guardian newspaper: “My mind was blown away when I read how he attacked a woman in 2005, both the tactics and methods he was using, the tools he had with him, to how well he had planned.
“I threw up, to be honest with you, because reading about it brought me straight back to my experience. ”
Scotland Yard detectives questioned Ms Behan and later told her they had contacted the Portuguese police. It appears that this led to the reopening of his case.
She said she was treated badly by Portuguese detectives, who dropped their investigation after eight months without identifying a suspect.
Ms Behan described her attacker as white, slim, blond haired, blue eyed and possibly German.
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According to the files, detectives could not find anyone in their files who matched the description, but that was not true.
In another Portuguese police file seen by Sky News, there are photographs of a young Christian B that fit the description.
They were taken away by police in 1999, five years before Ms Behan’s rape, after her arrest and deportation to Germany for sex crimes against children.
If police find evidence against Christian B for the attack on Ms Behan, he is unlikely to be charged as Portugal has a 15-year statute of limitations for rape investigations.