Protesters gathered outside the Cypriot high commission before marching through London chanting “we believe her”, on the eve of the sentencing of a 19-year-old woman convicted of lying about being gang-raped in Ayia Napa.

A judge last week ruled the teenager from Derbyshire wilfully indulged in public mischief in claiming she was raped by a group of 12 Israelis over the summer, then retracting her allegations 10 days later.

She is due to be sentenced on Tuesday morning and could face up to a year in prison and a €1,700 (£1,500) fine. However, during her trial she alleged that Cypriot police forced her to sign the retraction after an eight-hour interview with no lawyer or translator present.

More than 100 protesters stood outside the mission with placards and banners calling for holidaymakers to boycott Cyprus. “The message we want to send is to the victim herself, to say you are not alone, we hear you, we see you,” said Verity Nevitt, who helped to organise the protest.

“We’re also calling out Dominic Raab and Boris Johnson for doing nothing … There has been multiple human rights violations [in this case] and the fact that it’s happened to a British citizen anywhere in the world is an outrage.”

Reports claimed the Briton would be granted a presidential pardon, although constitutionally this could only be awarded after sentencing and would not overturn her conviction of indulging in wilful public mischief.

“She would still have to appeal that,” one well-placed government source said. “The president will not intervene until after the sentence and we have to wait and see what that is.”

If the teenager receives a suspended prison term she will be able to walk free and return home immediately.

Despite the hopes of a pardon, fears grew on Monday that the judge, Michalis Papathanasiou, would deliver a tough sentence.

“We are not optimistic at all,” said Susana Pavlou, who heads the Nicosia-based Mediterranean Institute for Gender Studies. “This is a judge who has been extremely aggressive in tone and attitude throughout court proceedings,” she said. “And his track record is poor in such cases. Our fear is that he will try to make an example of her.”

Papathanasiou gained notoriety for acquitting police officers accused of incompetence in the case of a Russian woman, Oxana Ratseva, who had been trafficked as a sex slave to the island and who subsequently fell to her death in mysterious circumstances in March 2001.

In 2017 he also refused to believe a local woman who had reported her partner raping her, arguing that her testimony was unreliable in court. The alleged assailant was acquitted.

More than 50 Israeli women, appalled by the treatment of the British 19-year-old, flew into Cyprus in a show of solidarity with Cypriot activists who have arranged a mass protest outside the court at the time of sentencing.

Some arrived at Larnaca airport wearing T-shirts emblazoned with the words: “We Believe You.” Others carried banners that declared: “You’ll never walk alone.”

Facebook Twitter Pinterest Sarah Maimon travelled to Cyprus despite breaking her leg in an accident recently. Photograph: Helena Smith

Sara Maimon, a 45-year-old Israeli nurse newly arrived from Jerusalem, said: “We are here to both protest injustice and support the victim. I hope it is meaningful to her that women in Israel believe her. There are people like me who also feel a little bit responsible that it was our citizens who did this to her.”

The Israeli women will also be demonstrating outside the Israeli embassy in Nicosia later on Tuesday. Protests are also planned in solidarity with the Briton in Tel Aviv on Tuesday morning.

At Monday’s protest in London, Dorothy Muir, a former police officer who during her career investigated sexual offences, said she had concerns about what she had heard about the woman’s treatment by Cypriot police. “Nobody should be interviewed for eight hours without a solicitor or an interpreter in a foreign country,” Muir said.

Protesters marched from the high commission, near Piccadilly, to Parliament Square, via Trafalgar Square and Whitehall, pausing briefly outside Downing Street. They ended their protest by the statue of the suffragette Millicent Fawcett.

There Nevitt read out a statement from the teenager’s lawyer before reading out details of the case, including the injuries recorded on her body, her testimony about her experience on the night, the DNA from semen found on her body, how the Israelis involved had circulated explicit sexual footage of her online, and how their relatives had sprayed champagne and chanted “the Brit is a whore” on their return to Israel after their release.

“The message sent is, if you are attacked and report, don’t expect help or justice,” she said. “The case won’t be properly investigated and you’ll become the accused. It also sends a message to men that you can get away with sexual assault. That you won’t even be investigated.”