Death of a British al-Shabab fighter
Last week the Somali Islamist militant group al-Shabab released an hour-long propaganda video - featuring a number of British men the group said had died fighting for it.
They included "Talha," a British-Asian man from Tower Hamlets in east London, who the video said had been killed last November.
Speaking in a noticeably British accent, he smiles at the camera while holding a rifle - and explains his motivation for being in the country.
"All the Muslims in Britain, especially the people of Tower Hamlets, the citadel I was born in. I call upon you to come to jihad," he says.
But who is "Talha" and how did he end up fighting - and dying - for al-Shabab, the group that has claimed responsibility for the Westgate attack in Nairobi?
BBC News has learnt that his real name is Taufail Ahmed. He was a British citizen of Bangladeshi heritage who grew up in Stepney Green in east London.
A number of British Muslims who knew him before he left for Somalia spoke to BBC News - but none wanted to be identified in case of repercussions.
One man, who described himself as a "former schoolmate", said he was "shocked and appalled" Ahmed had joined al-Shabab. He said he was giving a bad impression of British Muslims to the world. Another said he had thought Ahmed had left the UK to study religion in Egypt.
The al-Shabab recruit attended Stepney Green School - but during his teenage years he became involved with street gangs.
"He was a bit off the rails," said one former acquaintance. "He was involved in fights and turf wars between different areas. There would be fist fights and improvised weapons, like belts and baseball bats.
"He was a bit cocky. If there was a group of guys he would be at the front," added another.
"Growing up in Tower Hamlets, there wasn't much to do. No-one had any money. There were hardly any youth centres. Young men just hung around on the streets getting into mischief. It was like no-one cared about us."
But in his early 20s, they say, Ahmed became more religious, asking questions about his place in the world - and the politics of Muslim identity and the West. The man who had once worn designer clothes switched to traditional Islamic dress and grew a beard.
Initially they saw this as a positive thing - someone who had turned their back on a life of petty crime.
But they had grown up in an atmosphere in which many British Muslims were angry at what they perceived as unjust Western foreign policy in the Islamic world. Lectures by hard-line preachers were also popular, according to those who knew Ahmed.
"When we were in school it was all about Abdullah el-Faisal," said one - referring to a British-Jamaican preacher jailed in 2003 for soliciting the murder of Jews and Hindus.
"Cassettes of his lectures got swapped like trading cards," said another, adding the now-dead preacher Anwar al Awlaki had been another influence.
And so Ahmed became part of a small, discreet group of British-Asian Muslim men from around Stepney Green who had radical beliefs.
"It was chicken and chips jihad," said one acquaintance. "They would meet and discuss global politics in the Muslim world and what they could do to get involved."
They told the BBC he and some others from the group had begun to spend a lot of time working on their physical fitness. Only later did they realise that it could have been preparation to fight abroad.
One of the others in that group was another British man of Bangladeshi origin - Mohammed Shamim Ali.
In August 2008 Ahmed and Ali left for Somalia via Kenya along with another man - Muhammad Jahangir. None seemingly had any connection to Somalia - but they had gone to join al-Shabab. They were responding to a call from the group for foreign volunteers and they never returned to the UK.
There is no official statistic for the number of people from the UK who have gone to fight in Somalia. Security officials simply do not know for sure because it is difficult to know who gets into the country over the border from Kenya.
Research by BBC News has established the names of almost 50 people from Britain who have links to Al-Shabab and related organisations.
The 47 names compiled by the BBC are based on a combination of sources, including public records from courts in the UK and abroad and further first-hand research and accounts. The names are not a complete list of people from the UK suspected of having gone to the region to fight.
The research found security chiefs believed at least 32 of the identifiable individuals joined jihadists in Somalia - including Ahmed and other members of his cell.
BBC News has matched four of the names in its research to confirmed deaths in Somalia - but the true figure is likely to be higher. Typically, al-Shabab uses a nom-de-guerre to describe foreign fighters who have died, making it difficult to confirm real identities.
Raffaello Pantucci, from the Royal United Services Institute, sais al-Shabab's appeal was not restricted to those of Somali origin.
"There was a certain point in the mid-2000s where the struggle seemed to transform into something with a much more globalist appeal to it," he said.
"The result was we saw people from across Britain's Muslim communities being drawn back to participate into the fighting."
When Ahmed, Ali and Jahangir reached Somalia, they received financial support from Shabaaz Hussain, another man from east London. Last year he was jailed for raising thousands of pounds to send to the three men.
Hussain was helped by the Ali's twin brothers - Mohammed Shabir Ali and Mohammed Shafiq Ali. The group posed as genuine charity fundraisers in London to con unsuspecting Muslims in the East End into handing over cash. The twins have also been jailed.
Al-Shabab said Ahmed had met his death in November 2012.
The legal charity Reprieve, acting on behalf of his family, says its investigations suggest he was killed on 12 November during an amphibious assault on a fishing village in southern Somalia. A 12-year-old boy was also reportedly killed.
About 10 days after his death, police in London told his parents he had died in a gun battle but there had been no British involvement in his death and he had received a Muslim burial.
However, Reprieve says it wants to know more about reports that British personnel were involved.
Kat Craig, of Reprieve, said: "We have reason to believe that there are Somali eyewitnesses who identified those involved as British personnel and for those reasons we believe that further inquiries need to be made and that the family has quite legitimate questions that need to be answered."
One of the former schoolmates described the death as a "waste."
"He was used like a pawn" he said. "He thinks he's helping the Muslim umma [global community]. But he's doing a disservice to British Muslims, and Muslims worldwide."