In February 2015 three schoolgirls from Bethnal Green in London, boarded a Turkish Airlines plane at Gatwick and flew to Istanbul – the first leg of a journey towards Syria, where a rapid land grab by Islamist militants a year earlier had established a self-proclaimed “caliphate” in Syria and Iraq.

Kadiza Sultana, Amira Abase and Shamima Begum were 15 years old when they set out to join Isis. Within weeks all three girls were “married” to Isis fighters.

Five years later, Sultana is believed dead after a 2017 airstrike, Abase has been widowed and unaccounted for after recent bombing in Baghouz, eastern Syria, and Begum’s husband has been captured by Syrian forces.

Begum, now 19, is heavily pregnant, and says she has already buried two of her children. She is being held in a refugee camp and is desperate to return to the UK.

In an interview with The Times, Begum, who fled Baghouz and is now in al-Hawl camp in northern Syria, revealed what she has endured and witnessed during the collapse of Isis and its caliphate.

Timeline of the Isis caliphate Show all 19 1 /19 Timeline of the Isis caliphate Timeline of the Isis caliphate ISIS began as a group by the merging of extremist organisations ISI and al-Nusra in 2013. Following clashes, Syrian rebels captured the ISIS headquarters in Aleppo in January 2014 (pictured) AFP/Getty Timeline of the Isis caliphate Abu Bakr Al-Baghdadi declared the creation of a caliphate in Mosul on 27 June 2014 Timeline of the Isis caliphate Isis conquered the Kurdish towns of Sinjar and Zumar in August 2014, forcing thousands of civilians to flee their homes. Pictured are a group of Yazidi Kurds who have fled Rex Timeline of the Isis caliphate On September 2 2014 Isis released a video depicting the beheading of US journalist Steven Sotloff. On September 13 they released another video showing the execution of British aid worker David Haines Timeline of the Isis caliphate The US launched its first airstrikes against Isis in Syria on 23 September 2014. Here Lt Gen William C Mayville Jnr speaks about the bombing campaign in the wake of the first strikes Getty Timeline of the Isis caliphate Isis militants sit atop a hill planted with their flag in the Syrian town of Kobani on 6 October 2014. They had been advancing on Kobani since mid-September and by now was in control of the city’s entrance and exit points AFP/Getty Timeline of the Isis caliphate Residents of the border village of Alizar keep guard day and night as they wait in fear of mortar fire from Isis who have occupied the nearby city of Kobani Getty Timeline of the Isis caliphate Smoke rises following a US airstrike on Kobani, 28 October 2014 AFP/Getty Timeline of the Isis caliphate YPG fighters raise a flag as they reclaim Kobani on 26 January 2015 VOA Timeline of the Isis caliphate Isis seized the ancient Syrian city of Palmyra on 20 May 2015. This image show the city from above days after its capture by Isis Getty Timeline of the Isis caliphate Kurdish forces are stationed on a hill above the town of Sinjar as smoke rises following US airstrikes on 12 November 2015 AFP/Getty Timeline of the Isis caliphate Kurdish forces enter Sinjar after seizing it from Isis control on 13 November 2015 AFP/Getty Timeline of the Isis caliphate Iraqi government forces make the victory sign as they retake the city of Fallujah from ISIS on 26 June 2016 Getty Timeline of the Isis caliphate Iraqi forces battle with Isis for the city of Mosul on 30 June 2017 AFP/Getty Timeline of the Isis caliphate Members of the Iraqi federal police raise flags in Mosul on 8 July 2017. On the following day, Iraqi prime minister Haider Al Abadi declares victory over Isis in Mosul Getty Timeline of the Isis caliphate Members of Syrian Democratic Forces celebrate in Al-Naim square after taking back the city of Raqqa from Isis. US-backed Syrian forces declare victory over Isis in Raqqa on 20 October 2017 after a four-month long campaign Getty Timeline of the Isis caliphate Female fighters of the Syrian Democratic Forces celebrate in Al-Naim Square after taking back the city of Raqqa from Isis. US-backed Syrian forces declare victory over Isis in Raqqa on 20 October 2017 after a four-month long campaign AFP/Getty Timeline of the Isis caliphate Trucks full of women and children arrive from the last Isis-held areas in Deir ez-Zor, Syria in January 2019 They were among the last civilians to be living in the ISIS caliphate, by this time reduced to just two small villages in Syria’s Deir ez-Zor Richard Hall/The Independent Timeline of the Isis caliphate Zikia Ibrahim, 28, with her two-year-old son and 8-month-old daughter, after fleeing the Isis caliphate, on Saturday 26 January 2019 Richard Hall/The Independent

Within 10 days of arriving in Syria in 2015, Begum was married to Isis fighter Yago Riedijk, who had already been wounded fighting in Kobani, south of the Turkish border.

The couple lived together in Isis’ defacto capital Raqqa, but soon after their marriage he was arrested, accused of spying, and was imprisoned and tortured for six and a half months.

After his release, the couple remained in Raqqa, but Riedijk was no longer classified by Isis as a fighter.

“Mostly it was normal life in Raqqa,” Begum told journalist Anthony Loyd, adding that “every now and again” there would be “bombing and stuff”.

She said the first time she saw a decapitated head in a dustbin it did not faze her “at all”.

“It was from a captured fighter seized on the battlefield, an enemy of Islam. I thought only of what he would have done to a Muslim woman if he had the chance,” she said.

Meanwhile back in the UK, Metropolitan Police Chief at the time, Sir Bernard Hogan-Howe apologised to the families of the three girls, after it emerged the police had not warned of the likelihood the girls might follow a friend who had left the same school and gone to Syria a few months earlier.

The families said they would have done more to monitor their children’s activities.

It emerged the three girls had paid more than £1,000 in cash to a travel agent for their flights to Istanbul, and police said they had raised the funds in part by stealing and selling their own families’ jewellery.

In 2017 Begum, her husband and their first child – a girl named Sarayah – left Raqqa and moved to the edge of Mayadin – a town on the Euphrates River in east Syria.

While here she was wounded in an airstrike which killed a woman and a child in the house they were all living in.

Since 2014, over 14,600 strikes have been carried out by US-led coalition forces fighting Isis, which include Australia, Bahrain, France, Jordan, the Netherlands, Saudi Arabia, Turkey, the United Arab Emirates and the UK.

Strikes reached a peak in Syria in 2017. In August alone, over 1,400 airstrikes were launched against Isis targets in the country.

Isis’s territory diminished rapidly. Raqqa was recaptured by an alliance of Syrian Kurdish and Arab fighters in October 2017.

The Iraqi government announced the war against the militants was “over” in December 2017.

By the beginning of 2018 the US-led coalition said 98 per cent of the territory once controlled by Isis had been regained, with militants only remaining in a few isolated pockets.

Despite her husband’s assurances of eventual victory for Isis, Begum was sceptical. “I began to think that the caliphate might not survive after all,” she said.

The family moved again, to the town of Susah, between Hajin and Baghouz. By now Begum also had a son, but as Isis lost ground, airstrikes grew increasingly frequent until they were a “daily occurrence”.

Towards the end of 2018, aged eight months, her son died. He was ill, undernourished and there was no medical care available.

Just one month ago, her one-year-and-nine-months-old daughter Sarayah also became ill and died. She was buried in Baghouz – the remaining Isis-held town in the region the family had retreated to.

Shamima Begum, photographed as a teenager before she travelled to Syria (PA)

As well as the death of her children, this point also signalled the demise of the caliphate for Begum.

She said Isis commanders told families of foreign fighters they could either stay on to face the bombing in Baghouz, or make their way into the desert and escape as best they could.

Begum said she saw her husband of four years surrender to Syria’s SDF as they had walked out of Baghouz. That was the last time she saw him.

Despite the enormity of what she has endured, she told The Times: “I’m not the same silly little 15-year-old schoolgirl who ran away from Bethnal Green four years ago … and I don’t regret coming here.”

She believes the caliphate “didn’t deserve victory”, due to its own corruption and oppression, and her objective now is to return to Britain. She said she would “do anything required” to return to live with her third child.

In the past those who have joined Islamist militants and then returned to the UK have faced prosecution for terrorism offences.

But in 2015 Sir Bernard Hogan-Howe said the three girls would not face terror charges or be treated as criminals.

Assistant Commissioner, Mark Rowley, head of Scotland Yard’s counter-terrorism command, said at the time there was a “difference between the person running around northern Iraq with a Kalishnikov” and three schoolgirls who had been duped into travelling to Syria.

But as Ms Begum is now 19, she is legally an adult. If she was under 18, UK authorities could argue they still had a duty of care to her.

“As a British citizen she has a right to come home here,” Security Minister Ben Wallace said on Thursday. “We are obliged to make sure our citizens have rights, no matter who they are,” he told Sky News.

But he dismissed any suggestion of sending officials to meet Ms Begum, saying: “I'm not putting at risk British people's lives to go and look for terrorists in a failed state. Actions have consequences.”

Sir Peter Fahy, a retired senior police chief who was the leader of the Prevent terrorism prevention programme at the time the girls left the UK, told BBC Radio 4 if Begum was to now return, British authorities would first detain her and investigate whether there was enough evidence to prosecute her.

He said it was understandable why the government was “not particularly interested” in aiding her return.