Shamima Begum is among the estimated 900 Britons who travelled from the UK to join the murderous Islamic State - and now she wants to come back and have her baby on the NHS.

Terrifyingly, as their caliphate crumbles, at least 260 of them are still unaccounted for including dozens of jihadi brides.

The biggest nightmare for the security services is trying to keep tabs on battle-hardened maniacs.

Some 180 with UK passports were killed on the battlefield either by allied warplanes or in fighting on the ground.

An estimated 450 of them are believed to have returned to Britain, where they are kept under as close scrutiny as the security services can manage.

Only a handful have been prosecuted, mainly because of a lack of evidence about what they did to support ISIS' murderous regime.

Here we profile some of the more notorious Britons who went to Syria after the caliphate sprang up in 2014 - and their fates:

DEAD

Mohammed Emwazi/Jihadi John

DEAD: Mohammed Emwazi (picture above) , brandishes a knife in this still file image from a 2014 video

A barbaric killer who horrified the world when he starred in videos beheading orange-clad British and American hostages. Nicknamed ‘Jihadi John’, Emwazi was the most notorious member of the British IS gang known as the ‘Beatles’ who murdered 27 people. Kuwaiti-born Emwazi, 27, who grew up in west London, was finally obliterated in a US drone strike in November 2015.

Reyaad Khan

DEAD: Reyaad Khan (pictured above), a British citizen who died fighting for Islamic State

The former student from Cardiff appeared in a chilling IS propaganda video smiling, clutching an AK-47 assault rifle and urging terror attacks on the UK. David Cameron ordered an RAF drone strike that killed Khan, 21, and fellow jihadi Ruhul Amin, 26, from Aberdeen, in August 2015. Mr Cameron told the Commons: ‘My first duty as prime minister is to keep the British people safe.’

Sally Jones

DEAD: 'White Widow' Sally Jones (pictured above) was killed by a drone, according to the CIA

Travelled to Syria in 2013, aged 44, with her son Jojo, nine, who was forced to participate in IS propaganda videos. She recruited jihadis by boasting: ‘You Christians all need beheading with a nice blunt knife... Come here, I’ll do it for you.’ She and her son are believed to have been killed in a 2017 drone strike. Jones, from Chatham, Kent, married Briton Junaid Hussain –also recruited by IS – who died in a drone strike in 2015.

STILL IN SYRIA

El Shafee Elsheikh and Alexanda Kotey

Alexanda Amon Kotey, left, and El Shafee Elsheikh (rigth), who were allegedly among four British jihadis who made up a brutal Islamic State cell dubbed "The Beatles

Two members of the Beatles, they were captured in northern Syria in January 2018 and are being held by Kurdish forces. Elsheik, 30, is a mechanic whose family fled to the UK from Sudan in the 1990s. Kotey, 34, converted to Islam as a teenager. Both have been stripped of their British citizenship and are seeking to exploit the legal uncertainty about their future. The fourth supposed Beatle, Aine Davis, 35, has been jailed in Turkey.

Jack Letts

Jack Letts (pictured above), dubbed Jihadi Jack, was reportedly the first white British man to join Islamic State

Nicknamed ‘Jihadi Jack’, the British-Canadian went to Syria in 2014. Captured by the Kurdish-led YPG, he has been in prison in Syria for the past 20 months. Letts, 23, converted to Islam while at comprehensive school in Oxford.

Muhammad Saqib Raza

Muhammad Saqib Raza (pictured above) - 40-year-old NHS doctor from Leicester

The 40-year-old NHS surgeon from Leicester was captured by the Syrian Democratic Forces in January 2018 attempting to smuggle himself out the country. He was accused of trying to radicalise colleagues at NHS hospitals before he travelled to Syria in 2016. He told the SDF that he was not an IS fighter but worked as a medic in areas under the group’s control. He has pleaded with British authorities to repatriate him to face trial in the UK.

Ashraf Islam

Ashraf Islam (pictured above) previously said he had travelled to Syria in 2015 to help refugees

British-born Islam, 22, has been held for a year by Kurdish forces. He told ITV News that he travelled to Syria in 2015 to ‘help the Syrian people’, eventually making it to Raqqa. He claimed he later lost heart and surrendered.

Anwar Miah

Mohammed Anwar Miah (pictured above), British foreign fighter from Birmingham with Islamic State

Birmingham pharmacist was captured by Kurdish forces near Hajin, eastern Syria, last September. A video showed Miah, 40, blindfolded claiming he was a doctor and pharmacist. He said he had been in Syria for just under four years and claimed he had been working in hospitals since he arrived.

BACK IN THE UK

Imran Khawaja

Imran Khawaja, a British jihadi nicknamed "Barbie" who fled a Syrian training camp because he had "had enough" of conditions there

Former nightclub doorman, 31, from Southall, west London, was jailed for 12 years in 2015 after posing with severed heads in Syria. After finding out he had gone there, his mother begged him to come home, saying: ‘When are you going to grow up?’

Mustafa Abdullah

Mustafa Abdullah was sentenced to four and a half years in prison

He was jailed for four-and-a-half years in December 2015, but is now out of prison. After he returned from Syria, police found pictures of him posing with firearms. Abdullah, 37, told the Old Bailey: ‘I love guns. I cannot explain it. They look nice.’

Mounir Rarmoul-Bouhadjar

Mounir Rarmoul-Bouhadjar (pictured above) wearing a striped top and a beanie hat

He met a Syrian bomb-maker on the border with Turkey, then returned to UK where he was arrested in possession of a bomb manual. Rarmoul-Bouhadjar, 30, was jailed for three years in 2014.

Mohommod and Hamza Nawaz

Mohommod Nawaz (left) and Hamza Nawaz (right) were jailed for conspiring to attend a terrorist training camp in Syria

Brothers Mohommod, 35, and Hamza, 29, attended terror training camp in Syria in 2013. After their return, both were jailed in 2014 but are now free.

Mashudur Choudhury

The 31-year-old man from Portsmouth who planned to travel to Syria to carry out acts of terrorism

The 34-year-old from Portsmouth was jailed for four years in 2014 after returning from the conflict zone.