For almost four decades Jacqueline Niego had hoped that her brother’s killers would eventually be tracked down to face justice.

On August 9, 1982, André Niego was in Jo Goldenberg’s restaurant, then a popular Jewish venue, when at least three Palestinians detonated a grenade and opened fire on the people inside, killing six people and wounding two dozen others.

Like every year on August 9, Jaqueline marked the event last Friday too, but this time, commemorations were different.

Jacqueline has recently learnt that after the attack French authorities sealed a secret pact with the Palestinian group that is believed to have carried out the attack. The news broke out on the day of the memorial.

Former French intelligence chief Yves Bonnet testified in court in January that in 1982 he instructed subordinates to negotiate a deal with Abu Nidal, the leader of a Palestinian splinter group. If the group pledged not to attack French targets again, the authorities would not prosecute those who had ordered and carried out the Rosiers Street attack.

“We gave them our word that we would not prosecute them,” Mr Bonnet reportedly testified in a hearing, saying he reported his talks to President François Mitterrand’s office.

Two other intelligence officials refused to testify, saying the case was classified, but said they cannot deny there had been contacts with Abu Nidal.

“Denying would be a lie,” François Clair and Louis Caprioli said in a hearing, according to the Le Parisien newspaper.

Victims and their families were shocked by the news.

“It’s deeply disturbing to learn our country sealed a deal with those killers,” Jacqueline Niego told the JC during a memorial.

The families had regained hope in 2015 where a judge, Marc Trevidic, identified four suspects: three perpetrators and the man thought to have planned the attack. But Norway, Jordan and the Palestinian authorities have refused to extradite them.

“I’m 80 years old now and I have little hope of ever getting justice for my beloved brother. I lose hope every day,” said Ms Niego.

“During the war the Nazis tried and failed to kill my brother. Those terrorist murderers did it.

“During the war I was only a toddler and André was my big brother whom I loved so much. He was six years older than me. We survived because I was hidden with my sister in a convent and he was hidden by priests.”

Their mother was killed in a concentration camp.

At the memorial, the French Association of Terrorism Victims called on French authorities to apply diplomatic pressure to obtain an extradition.

One of the memorial’s organisers, Yohann Taieb, pointed out that Nidal's group was already planning new attacks in Europe as French Intelligence negotiated with him: “Yves Bonnet said the pact worked and that it wasn’t his problem if Abu Nidal struck other countries like Italy.

“I don’t know if that was some kind of dark humour, but several months after the Rosiers street attack, Abu Nidal did attack Italy. [His followers] attacked a synagogue in Rome.”

A two-year-old toddler was killed and dozens were injured in that October 1982 bombing and shooting at the entrance of the Great Synagogue of Rome.