The British documentary maker Sean McAllister made headlines in 2011 when he was seized by the Syrian secret police. His capture meant the couple he was filming at the time had to flee the country, but that didn't stop them making the documentary together after his release.

Spoiler warning: Details of the film A Syrian Love Story are revealed

From his prison cell, Sean McAllister could hear the screams of Syria's revolutionaries. It was October 2011 and the country was slipping deeper into war. McAllister, a film-maker, had been jumped on by secret police in Damascus, blindfolded, and brought to the prison, where he became a witness to the regime's brutal treatment of protesters and activists.

"There's a sort of softening-up torture, with these 20-year-old kids with inner tubes and cables and they just whip and whip and whip, and you just hear people screaming in different rooms," he recalls. "They do that for a couple of hours before they bundle them into windowless dungeons where there's hardly enough room to sit down."

When he was released, McAllister's testimony made headlines, but at the time his thoughts were focused on the family he had been filming for a documentary, which is now on release in the UK. A Syrian Love Story follows two married activists, Amer Daoud and Raghda Hasan, and their children over a five-year period.

When McAllister was detained in 2011, the authorities took his equipment, which contained footage of the couple speaking out against the regime and organising protests. But when the police demanded to know where they were, McAllister misdirected them, giving Daoud and Hasan time to flee to Lebanon.

"At that point I felt terribly guilty, but then after that for the next year it was terrible, because they were then suffering, stuck in Beirut," says McAllister.

Having become very much part of the story, McAllister continued to film the family - and they did nothing to stop him.

"I actually thought Sean was a window of hope," says Daoud. "Because we are political activists. As political activists you have a higher goal in life, you have a message that you want to convey and communicate as well."

Image caption Sean McAllister and Amer Daoud

McAllister had arrived in Syria in 2008, seeking a break from his work in war zones and curious about life in what he calls a "functioning dictatorship". For eight months, he searched for a story that would allow him to get beyond the picture-postcard image of Syria that officials presented to tourists. Then, one night in a park in Damascus, he met Daoud, who told him: "If you really want to make a film about Syria, come and film me."

McAllister had found his story about Syria - and it was a love story.

A member of the Palestinian Liberation Organisation, Daoud had spent three years in prison, where he had formed a relationship with the woman in the adjacent cell. Raghda Hasan's background was very different - she came from the same Alawite sect as the president - but she was also a dissident, a communist revolutionary. The two made a small hole in the wall separating them and, after months of communicating through it, they fell in love. When they were released from prison, they got married and had two children together.

"All we wanted was to be together all the time - and nothing would separate us, even death," recalls Daoud.

But at the time McAllister met him and his children, Hasan was in prison once again for writing a novel based on the couple's relationship, among other things.

Media playback is unsupported on your device Media caption Daoud and Hasan's son Richard describes his hatred for the president

Hasan was released again in 2011 as part of an amnesty, one of the Syrian government's responses to the Arab Spring.

But not long afterwards, the family had to make their escape to Lebanon and it was there that the marriage began to break down. Unable to live at a distance from the revolution she had longed for and worked towards, Hasan returned to Syria. And without her, her husband and children were unable to seek asylum in Europe.

The family eventually reunited and sought refuge in France, but exile - the life of the refugee - did not bring happiness.

In long, claustrophobic scenes shot in the couple's apartment - the Sheffield documentary festival, which awarded the film its top prize earlier this year, drew parallels with the work of Ingmar Bergman - the viewer is witness to the couple's rancour and mutual recrimination. There is an affair. There is a suicide attempt.

Find out more

Listen to Sean McAllister and Amer Daoud speaking to Outlook on the BBC World Service

A Syrian Love Story is in UK cinemas now and will be on BBC television in the UK on 28 September

"It was bizarre," says McAllister, "because they were in Albi, this idyllic, beautiful place in the south of France, which is I guess the dream - and I was thinking back to the beginning of this journey, when they'd been dreaming of freedom and in this bizarre kind of way, this was freedom.

"But in getting there they'd lost so much and each other - and they couldn't make sense of themselves or where they were."

They began to look to McAllister to make sense of it all for them. They both rang him regularly, asking him to come to France to act as a prosecuting counsel or judge in their quarrels. Instead, he was a witness, albeit one with powers to cross-examine.

"When you were a prisoner, he loved you," McAllister reminds Hasan at one point. "All Syrians love prisoners," she replies.

"No," McAllister says, "he loved his wife."

Media playback is unsupported on your device Media caption Daoud and Hasan are asked if they love each other.

Again and again, we see the family reviewing McAllister's footage from 2010 and 2011 - a record of their earlier family life that doubles as a reminder of the country they had left behind and of friends and relatives who had been killed.

Hasan now lives in Turkey, where she has a role in Syria's opposition government. Daoud still lives in France, along with the children. He watched the final cut of McAllister's film on a laptop in a cafe.

"When I watched the film, I thought: 'There's me, there's my wife and my children.' And I couldn't hold back my tears," says Daoud. "I cried for hours and hours on my own, just feeling sorry for myself and my life, feeling sorry for my children, feeling sorry for Raghda. What is now and what could have been - all these thoughts were just going through my mind for days after watching the film."

Daoud believes that his marriage would not have broken down if Syria had been at peace. "I'm sure," he says, "because we have a great love story."

When McAllister began filming in 2010, he could not foresee the Arab Spring or the civil war. He worked on the film as a "labour of love" without a commission from a network until 2013. Then, in the last few weeks, just in time for the film's release, came another unexpected development - the sudden upsurge of public interest in the plight of Syrian refugees.

Sean McAllister and Amer Daoud spoke to Outlook on the BBC World Service. Listen again via iPlayer or get the Outlook podcast. A Syrian Love Story will be screened by Storyville, on BBC Four, on 28 September.

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