London, Jan. 5: The British security services trying to identify the man in the latest Islamic State execution video think it could be Siddhartha Dhar, a 32-year-old Indian-origin Hindu who converted to Islam a decade ago.
He took on the name Abu Rumaysah and fled to Syria in 2014 with his family.
The video in which five victims alleged to be "British spies" are shot in the back of the head has the hooded man brandishing a gun, calling David Cameron an "imbecile", threatening the UK and speaking with what has been deciphered as a "British accent".
In interviews with newspapers and television yesterday, Siddhartha's sister, Konika, gave conflicting evidence.
Referring to Siddhartha, Konika conceded the man in the 10-minute video did sound "a bit like him" before adding she did not think it was her brother.
Konika added: "If it is him, bloody hell am I shocked? I am going to kill him myself. He is going to come back and I am going to kill him if he has done this. I can't believe it. This is just so shocking for me. I don't know what the authorities are doing to confirm the identity, but I need to know if it is."
Konika had earlier said that the family traced its roots to India. The surname is popular in Bengal but it is not clear whether the family is of Bengali-origin.
"Our parents were born in India and came to Britain when they were children. We respected our Hindu heritage and observed its traditions, but we were not extremely religious. Sid, whose full name is Siddhartha, was a good basketball player and supported Arsenal football club. He listened to (American rock bands) Linkin Park and Nirvana," Konika told The Sunday Times, London, last year.
She explained how things changed. "Then, when Sid was 16, our father died at the age of 46. I've wondered sometimes if what happened later could have been partly because he lacked a male role model after Dad died. Sid had a wide group of friends from different backgrounds, but he began seeing more of one friend in particular. Mizanur Rahman was the son of Bangladeshi immigrants; Sid had known him since childhood."
Konika went on: "I later learnt that Rahman would say things to my brother such as, 'We can die at any time. There is no point in delaying converting. Only Muslims can go to paradise.' I believe he put pressure on my brother to convert."
"The process was so gradual," she noted. "It crept up on all of us until it seemed impossible to stop. Slowly, Sid changed his appearance. He grew a beard and began dressing differently. One by one, he stopped seeing his non-Muslim friends and then even those Muslim ones who were not sufficiently devout."
She remembered a significant moment. "We only knew for sure that he had converted when our mother received a telephone call one day in 2002.
"Sid, then 19, had been arrested at a pro-Palestinian demonstration. When Mum picked him up from the police station he told her that he was now a Muslim and had taken the name Saif al-Islam, which means 'sword of Islam'. But he assured her that he wasn't involved in radical religion. We were worried about the arrest, of course, but we were a liberal family. Why shouldn't Sid become a Muslim if he wanted to?"
Later, Siddhartha got married. "I hoped that becoming a father himself might change Sid - and it seemed to at first. He had married Aisha in 2006 and they had their first child, Rumaysah, two years later. Abu Rumaysah means 'father of Rumaysah': I only learnt about Sid's new name when I saw that picture last November."
Last year, after a month in Syria, he tweeted a picture of himself from the part of the country held by the Islamic State. In one hand he held a baby, and in the other an AK-47. He called himself "Abu Rumaysah" and used the hashtag Generation Khilafah - a reference to the so-called caliphate.
Speaking at their home yesterday, their mother Sobita Dhar too gave slightly contradictory answers: "These are the most difficult questions to answer - I just cannot say (whether it's my son). I'm not sure within myself.... I last saw him before he went off to Syria two years ago."
Asked whether she had noticed any extremist tendencies in her son before he left, Sobita said: "Nothing. Nothing of that. Nothing whatsoever."
The militants released a film showing the five accused of spying kneeling on the ground in orange jumpsuits before they were shot dead.
Asked what she would say to her son, Sobita said: "It depends on what he says to me, on whether it is true or not. As far as I know, I am sure about his character. I definitely know him as a good person, no doubt about that."
The security services, equipped with facial and voice recognition techniques, have plenty of material on Siddhartha, who was once openly active in militant Islamic circles in London.
Back in September 2014, Siddhartha was among a group of eight men arrested along with their leader, Anjem Choudary, a Pakistani-origin "radical" who often appears on television to make outrageous statements.
Siddhartha, who apparently converted to Islam after being "radicalised" by Choudary, would himself sometimes appear on television to support the extremist cause.
There was a time when Siddhartha ran a business in London, renting out bouncy castles for children.
For example, he was interviewed on the 60 Minutes programme on CBS News and told presenter Clarissa Ward that he was unable to love his mother because she was not a Muslim.
Speaking to ITV News, Choudary rejected criticism that he "warped the mind" of Siddhartha, saying: "If warping someone's mind and not being on a rightful path is believing in the shariat and wanting to bring your children up according to the shariat, then I am very happy to warp everyone's mind."
In a 2013 interview with Vice News, Siddhartha had himself talked about his conversion after 9/11 and described Cameron and MPs as "the real preachers of hate and violence... who are allowing soldiers to fire bullets of extremism at men, women and children in Afghanistan".
Barely 24 hours after being released on bail, Siddhartha, his pregnant wife and their three other children caught a bus to Paris from where they made their way to Syria. How the closely-watched family from Walthamstow in East London slipped the net has never been satisfactorily explained.
After a month in Syria, he boasted how he had fooled MI5, the British intelligence service: "My Lord made a mockery of British intelligence and surveillance."
Konika expressed the family's anguish at the time: "Words can't describe how I feel and I'm absolutely devastated."
Since his flight to Syria, Siddhartha had fallen off the radar - until the release of the latest Islamic State video a couple of days ago.
Yesterday Konika said her memories of her brother were from when they were children and teenagers, and that she had barely heard from him since he went to Syria to fight. He had not responded to her emails and calls, though he has spoken with their mother occasionally.
A whole generation of young Muslim men in the West were radicalised by President George W. Bush's "war on terror" following 9/11 and the subsequent invasion of Afghanistan and Iraq. It is estimated that more than 800 Britons have travelled to Syria and Iraq to fight for the Islamic State, including families from Luton, Bradford and London.
But Siddhartha appears to be the first Hindu to have converted and joined the extremist cause.
"He was a very pleasant boy, and I know it may be hard to believe but he still is, and I still believe that he still can be that person," Konika said.
"I think it is important for him to realise and understand the person that he has become, and I want him to question himself and his actions in what he is doing, and to question whether this is truly him and what he really wants.
"I am still convinced that he doesn't really want to be involved in this, and I feel a bit guilty for what has happened, that I haven't done enough to stop things. If there is anything I can do I would like to do it. I still really miss him. He is still my brother and he will always be my brother, and I will always be his sister."
She condemned the threats made in the video. "I don't know if it is him (her brother), and I hope it is not, but if it is, worst case scenario, then he has made a direct threat to the Prime Minister (Cameron), which is terrible and awful."
In the latest video, before killing the prisoners in cold blood, the man warns Cameron that "your children will pay" for British airstrikes on IS targets in Syria - there have been only three bombing sorties by the Royal Air Force.
Konika pleaded with the government to help provide an alternative route for foreign fighters like her brother.
"I think it is really important for both the families that are left behind and also the fighters out there to know that they do have another option. From the way that I see it, it looks as though essentially what we are saying to these foreign fighters is that you have got two options - you can either kill or be killed, because they don't have an alternative option."
Konika said she felt "some sort of sympathy" for them, and that if there was an option to help her brother return to the UK she would "love to take up that challenge and perhaps work towards de-radicalising him".
She went on: "I just don't think that there is a way out for them. Once they are trapped in this movement, what option are we giving them? He is still British, regardless of what he says, and if he is going to be targeted, give him an option to come back.
"It is something that we need to consider in terms of our government. They have no other option, especially when you are involved in an organisation as dangerous as the IS. If you leave the organisation, as I understand apostasy is the punishment - it is death. So really they have got no option, they can either kill other people or be killed."
But the chances are that there is now no way back for the man in the video.
The masked executioner in the video bears a resemblance to the Islamic State's former executioner-in-chief, who was nicknamed "Jihadi John". He was killed by a US drone strike near an iconic clock tower in the terror group's de facto capital of Raqqa in Syria in November 2015.
