Gabriel was our angel, say parents who vow for justice over French student

Francoise and Olivier Ferez also urged Gabriel's killers to turn themselves in to the police.

The couple from Prouzel, near Amiens, in France, then warned the perpetrators they would not rest until they were brought to justice.

Magali Bonnans, the devastated girlfriend of murdered Gabriel Ferez

Last night detectives continued to question a 21-year-old man over the double murders of Gabriel and his friend Laurent Bonomo last Sunday.

The biochemistry students were found stabbed, tortured and badly burned after a fire at a flat in New Cross, South London, where Mr Bonomo was staying.

A pathologist found 243 separate stab injuries on their bodies. It is believed that the students, both aged 23, were dead before the fire was started.

Mr Ferez snr, a nurse, and his wife were joined by Laurent Bonomo's parents in the UK early last week to identify their sons' bodies. Both couples returned to France, where the Ferezes released their statement yesterday.

It said: 'To those who committed this crime we say: it is possible you did not anticipate how this might turn out. We plead with you to turn yourselves in. We will not leave you in peace.

'We ask our friends the British people, please HELP us. If you know of anything unusual or suspicious that may help in this investigation please report this to police. We ask that you protect your children. It is too late for Gabriel, an angel who gave us 23 years of love.'

The Metropolitan Police confirmed a man was arrested in the street at 3.40am on Saturday. He remains in custody in South-East London.

Mr Ferez, who lived in South Norwood, travelled to Mr Bonomo's flat in Sterling Road, New Cross, to watch the final of football's Euro 2008, and play computer games.

Officers believe two Sony PSP games consoles were stolen.

Mr Ferez's devastated girlfriend Magali Bonnans, a 23-year-old student, has spent the past week staying with her boyfriend's best friend Antoine Galloux and his family in France, too grief-stricken to come to London.

She met Mr Ferez two years ago when both were students on the same molecular science course at the Clermont-Ferrand Polytech in Central France.

Mr Ferez and Mr Bonomo, from Velaux, near Marseille, were working on a placement research project at London's Imperial College.

Anyone with information should call police on 020 8721 4155 or Crimestoppers on 0800 555 111.