A Greek coach pleaded not guilty to raping an 11-year-old athlete on Wednesday, implying that their relationship had been consensual and telling his trial that they planned to marry with her family's knowledge.

Triantafyllos Apostolou, 38, took the stand at the start of what has been hailed a landmark trial in Athens and the first major court case in the country of 10 million to emerge in the #MeToo era.

Apostolou has been charged with multiple rapes, assault on a minor and the corruption of a minor between 2010 and 2013. If convicted he could face up to 20 years in prison.

The case emerged after a Greek Olympic gold medallist, Sofia Bekatorou, spoke publicly in 2020 about her own abuse, prompting an outpouring of testimonies from athletes in Greece, including the plaintiff in Wednesday's trial, now aged 21.

The plaintiff, who is not being named at her family's request, says she was assaulted in 2010 by her sailing coach Apostolou, who was around 26 at the time.

She has told Greek television that she was "systematically raped" by Apostolou, and "physically and verbally abused" by him from the age of nine.

"It took me 10 years to understand that a child cannot be at fault," she told ANT1 TV.

On Wednesday, the three judges presiding over the trial authorised her to testify behind closed doors without media present on January 26, when the court resumes.

Taking the stand, Apostolou entered a formal plea of not guilty and defended his relationship with the then 11-year-old. The age of consent in Greece is 15.

"It happened several times," he said. "Would you consider it rape when it happened many times?"

"We intended to get married and our two families were aware. You will see. During the trial, it will be proven."

He effectively identified himself as the accused when he gave an interview last year, claiming that the sex had been consensual.

"We were to be married and her mother had agreed," he told the Proto Thema daily.

But prosecutors say Apostolou, who is in pre-trial detention, "used sexual but also psychological violence against the minor so that she would not reveal her rape to her parents".

A small number of protesters demonstrated outside court in support of the plaintiff, holding placards that read "We are full of rage".

Sofia Bekatorou (for right) arrived at court with her family
Sofia Bekatorou (for right) arrived at court with her family AFP / Louisa GOULIAMAKI

Her family had initially wanted to avoid the publicity of a trial, but the plaintiff said she had been "given courage" by Bekatorou and hoped her own case could encourage more victims to come forward.

"We must break the silence, punish abusers and end any stigma towards victims of sex abuse," she told ANT1 TV.

Bekatorou, a gold medallist at the 2004 Athens Olympics and a witness in the case, did not speak to reporters as she arrived at the courthouse on Wednesday.

She herself claims that she was subjected to "sexual harassment and abuse" by a senior sailing federation official after trials for the 2000 Sydney Olympics when she was 21 years old.

Her revelations led to other Greek women speaking up about alleged assault, and more than three years after it started in the United States, the #MeToo movement took off in Greece.

The past year has seen a flood of accusations of sexual assaults suffered by female athletes, students, journalists and actresses, some of whom say they were still minors when the attacks happened.

As Bekatorou's allegations of abuse date back more than 20 years ago, they fall outside the statute of limitations in Greece and cannot be prosecuted.

But her actions have already brought about change.

Prime Minister Kyriakos Mitsotakis has praised her for speaking out, saying she helped create awareness about the longstanding issues of sexual harassment and assault.

Faced with the scale of the problem, the conservative government has introduced tougher penalties for sexual abusers and extended the statute of limitations for the abuse of minors, as part of a package of measures.

The authorities have also set up an online platform for reporting incidents in real time and telephone help lines for victims.

Last September, Greece introduced sex education courses -- including the concept of consent -- into public schools for the first time.

But Bekatorou herself insists much remains to be done.

"The #MeToo movement continues," she told Marie-Claire magazine in a recent interview. "It is alive because of the great number of victims of abuse."