His son was a Bataclan terrorist; my daughter was killed there. Now, we've written a book together

His terrorist son may have killed the other's daughter at the Bataclan, but an unlikely bond has since formed, finds Henry Samuel.

Two fathers sit in a dark Parisian cafe sipping drinks and conversing quietly. Both have suffered a parent's worst nightmare: losing a child in the prime of life with no time to say goodbye. Their children were both 28 and died on the same day, November 13, 2015, in the Bataclan concert hall in central Paris.

Yet an apparently unfathomable gulf separates their fates. One was shot dead by an Islamist in France's worst terrorist atrocity in modern history. The second was one of the murderers.

Knowing this it is strange, extraordinary even, to see Georges Salines smile at Azdyne Amimour and touch his arm as he would an old friend. Where one would expect anger and recrimination against a man who raised one of France's most notorious mass murderers, there is only warmth and bonhomie. "It's true that seeing the fathers of a victim and assailant together is something of an oxymoron, a contradiction in terms" says Amimour, 72, in a blue cap and goatee as he takes a drag from a cigarette.

Yet not only are the two men on speaking terms, they last week released a book of their exchanges called Il Nous Reste les Mots (We Still Have Words). Salines's daughter Lola, a children's books publisher, was gunned down on a balmy evening alongside a friend who had called at the last minute to say she had a spare ticket to a rock concert. American band Eagles of Death Metal launched into a song called Kiss the Devil, Amimour's son Samy strode into the hall with two other Kalashnikov-wielding terrorists and proceeded to pick off hapless attendees in a 20-minute bloodbath.

Meanwhile, other members of the commando, who claimed they were avenging Western-caused deaths in Syria in the name of Islamic State, wreaked carnage in a string of nearby bars and restaurants in eastern Paris. An attack on a football stadium outside the capital was foiled. By the end of the evening, some 130 people had died, including 90 at the Bataclan. Lola died from three lethal gunshot wounds. Samy was shot by the first police officer on the scene before actioning his suicide belt. Azdyne first contacted Salines in February 2017, when the latter was president of a victims' group called 13onze15 (the date of the Paris attacks).

"I said what do you want?," Salines recalls in the book. "He said: 'I, too, feel like a victim and want to explain myself'." At first sceptical and worried what other families might think, Salines eventually agreed but took along Aurélia Gilbert, a survivor of the attack and co-founder of the association. Both write that any mutual misgivings dissolved; Salines was impressed by Amimour's "humanity, love of life, tolerance" and the terrorist's father of the other's warmth and open-mindedness.

But they had deeper motives to consider. "Personally, I wanted to understand the reasons that led people the same age as my daughter to commit this atrocity," says Salines, who began his career as a doctor before working in public health management. "How does one become a terrorist?

"There was a political motive too. I wanted to send a message to French society, which is if us two can talk to each other, all is not lost." Salines remembers his daughter as "full of life and energy," interested in sport, music, books and travel. "She had a huge ability to make high quality friends. She was someone who was very generous... She had this ability to accept people without judging them."

What would she have made of this book? "I can't speak for the dead but in my heart, I'm sure she would have totally understood." Amimour, who owns a vegetarian cafe in the Belgian city of Liège, "hoped to lift the lid on radicalisation." The two fathers do not see eye to eye on everything, however. "When Samy was small, he was adorable, kind, shy - an angel," said Amimour. "He didn't know how to say no so we nicknamed him 'Oui' (Yes). 'Are you coming with me Samy? Yes. Do you want to sleep the night here? Yes.' He was very easy to influence. That may have been his downfall. "I'm a victim and he was too, of manipulation."

"That doesn't stop him being guilty," Salines retorts. "We are always the fruit of our upbringing, education, people who we meet, but we have our own free will and can resist manipulation." "But you can't always resist," replies Amimour. "I did despite living through poverty, humiliation, disdain, racism, prison at 11 years of age in Algeria. I took another path. But others cannot." Worldly, cultured and a moderate Muslim who "dressed up as Father Christmas" for Samy and his two sisters and taught them to uphold the values of the French republic, it is hard to comprehend how Amimour could have spawned a fanatical monster.

He moved to France in the Seventies where he met his wife, Mouna, on a Paris-bound plane. "She was reading the Koran. I don't know if it was out of belief or fear." Following spells in the film and music business, he managed a Paris brasserie before running a clothes store and moving to the multicultural suburb of Drancy. "I'm still struggling to find reasons. He had everything in his childhood, all the things I didn't have. It's true I travelled due to work but I can't say I was an absent father," he tells me. Samy was a good student and passed his baccalaureate first time and started a law degree, but there were early signs of unhappiness when he told a doctor at 15 that he didn't like the fact his parents didn't pray.

After spurning his father's attempts to get him to study theology in Belgium, he appears to have fallen under the sway of extremist preachers on the internet, notably Fouad Belkacem, former head of Sharia4Belgium, a radical outfit intent on turning the country into an Islamic state. In 2012, police raided the family home in Drancy and arrested him on suspicion of links with terrorism and planning to go to Yemen and Pakistan. Then, in September 2013, Samy vanished. Days later, he contacted his mother on Skype to announce that he was in Syria to fight jihad against the Assad regime. "Don't come and look for me," he said. "All is going well."

Desperate to save his son, Amimour risked his own life to travel to Syria, just as the caliphate was being proclaimed. However, he received a stony reception and returned home feeling "powerless". He had heard nothing for months until anti-terror police arrested him and his wife and daughter after the attacks, informing him that Samy had slipped back into France undetected and had died during the Bataclan onslaught. "I did not shed a tear," Amimour writes in the book. "I felt a mix of sadness, hatred, anger, tiredness and thanklessness." Does he feel guilty for the atrocities his son carried out?

"Of course I do," says Amimour, who wrote a letter to Lola in which he and his family apologised "a thousand times" for his son's crime. "Did Samy turn to the bad because of me?," he asks in the book. "No-one will ever know." Amimour has never privately discussed his son's murders with his wife since he died; curious, surely, given the book's focus on talking. "My wife is a bit like Samy when he was young: shy, kind and very sensitive. I don't bring it up so as not to rub salt in the wound," he explains. "The only time she has talked is in George's presence. He has lifted a great weight and brought us so much."

Smiling, Salines turns to his unlikely co-author and notes that, in the week marking the fifth anniversary of the attack on satirical magazine Charlie Hebdo, "Upholding the freedom of expression is essential.

"Terrorism is all about trying to shut people up. We must keep talking."