The British ex-girlfriend of Christian Brueckner has been interviewed by German police investigating Madeleine McCann’s disappearance.
And the 45-year-old was told she would be a crucial witness if they get the suspect to trial.
Detectives flew to the Algarve where the barmaid lives and questioned her over her relationship with the paedophile, who they believe abducted and murdered the toddler in May 2007.
She is still too scared of her ex to reveal her identity as he allegedly terrorised her while they were a couple and she lives in fear he will one day be released.
But in a major escalation of their investigation the officers reassured her that Brueckner will be behind bars for a lengthy period.
A friend of his ex told the Mirror: “They told her not to worry about him being released.
“They said he’s going to be inside for a very, very long time. She sat down with them for 12 hours. It was gruelling and upsetting for her. She was really upset but they reassured her, saying she was an important character witness.
“They had wanted her to go to Germany and meet them and said they would pay for flights and a hotel.
“But she didn’t want to leave, so two detectives flew to Portugal to meet her instead.
“They wanted to know everything she knew about Christian and all about everything he did to her. They said every little detail about him was useful to help analyse behaviour patterns.”
Last month’s interview with the barmaid was the first time German police have been allowed to work on the case in Portugal. Three Portuguese officers and two translators also sat in on the interview in Faro. Portuguese police have previously interviewed her.
And former colleagues at the Lagos bar where she worked with Brueckner have also been interviewed by police. Prosecutors in Germany are desperate to build a case against Brueckner, 43.
They claim to have proof Madeleine is dead but do not have enough evidence to charge their suspect at the moment.
The Mirror revealed in June how he is alleged to have repeatedly tormented his ex, who is originally from Berkshire, when they dated in 2004 and 2005. He allegedly broke into her flat through a window and lay in wait for her under her bed.
The alleged incident took place hours after he brutally attacked her in a jealous rage because she innocently hugged another man.
Brueckner allegedly repeatedly slammed her head against a wall in the ladies toilets of the Algarve bar where she worked – leaving her a bloodied mess.
When she returned home she had a “horrible feeling” someone was inside and found him hiding. She believes he was lying in wait to attack her if she brought another man back. Instead the rapist, then aged in his late 20s, stared at her and said “goodbye” before fleeing.
Madeleine was three when she vanished from her family holiday apartment in Praia da Luz while parents Kate and Gerry dined out with friends in a nearby tapas bar.
In June Brueckner, who lived in Praia da Luz at the time, was named as a suspect in the case by German authorities but he denies any involvement. He is serving 21 months for drug offences in Germany.
Brueckner was convicted last year of raping a pensioner in the resort in 2005.
He is expected to begin a seven-year sentence once his appeal process is exhausted. There were fears he could be released on a legal technicality but a European Court of Justice lawyer advised he should remain behind bars.