NAIROBI (Kenya): When a group of masked and heavily armed fighters rampaged through a Kenyan shopping centre last Saturday, shooting dead scores of shoppers, one question for the tabloid media became irresistible: had they been funded, perhaps directed, by a 29-year-old British mother?

When a number of witnesses described a white woman among the terrorists, was it Samantha Lewthwaite they had seen, the youngest daughter of a British soldier from Aylesbury, southern England, the shy, gawky schoolgirl who “all the teachers loved”?Those questions have been preoccupying investigators — as well as the media — since the attack on Nairobi’s Westgate mall, for which the Somali jihadist group al Shaabab claimed responsibility. Lewthwaite was nicknamed the White Widow after it emerged last year that the Muslim convert, who was married to the July 7 bomber Jermaine Lindsay at the time of the 2005 attacks, was being hunted by Kenyan police in connection with an alleged 2011 bomb plot.

Lewthwaite had expressed shock after the London bombings, saying she “totally abhorred” her husband’s actions and telling journalists she and the couple’s two children were “victims as well”. But she disappeared before resurfacing in Kenya as an important member, according to counter-terrorist officials, of the Somali terror group. Handwritten notes found by the Kenyan police in 2012 and attributed to her claimed her children wanted to become jihadi fighters.

Who is Samantha Lewthwaite and, more urgently, where is she now? Despite the firestorm of interest in Briton since the Nairobi atrocity — fuelled on Tuesday when Kenya’s foreign minister said a British woman who had “done this many times before” had been involved, and by Interpol issuing an international warrant for Lewthwaite’s arrest — the Kenyan prime minister has admitted he had no concrete evidence of her involvement in the shopping mall slaughter. Privately and in public, security sources in Britain and Kenya have cautioned against jumping to conclusions. Stig Jarle Hansen, a Norwegian academic and security adviser who has written extensively on the Somali terror group, agreed, saying: “This is a mother on the run with little military or technical expertise, certainly compared to a lot of al Shabaab activists, some of whom have been in the battlefield for 10 years. Why would they use a person like that [for this kind of attack]?”

But as the Interpol red notice demonstrated, Lewthwaite’s arrest is a priority for the authorities in Kenya and the British anti-terrorist officers assisting them. “We cannot rule out that Lewthwaite played a role in this,” one international intelligence source told the Guardian, saying female al Shabaab sympathisers played an “essential role” in funding and supplying terrorist cells in Somalia.

Lewthwaite spent her earliest years in Banbridge, Northern Ireland, where her English soldier father Andy married a local woman before the family moved to Aylesbury in Buckinghamshire. Schoolfriends have spoken of a popular and “very, very clever” girl who as a teenager went to a lot of parties, before becoming increasingly interested in religion, and finally converting to Islam in her late teens.

She had enrolled at university in London when she met Lindsay at an anti-war demonstration, and the pair married in 2002 when she was 19 and he 17. She was eight months pregnant with their second child when he blew himself up on a Piccadilly line train killing 26 people.

Senior detectives who interviewed Lewthwaite after the bombings say they saw nothing to indicate she had been radicalised, though she had met her husband’s fellow bomber Mohammed Siddique Khan. She returned to Aylesbury, but began travelling abroad a lot, according to a friend. In 2009 she gave birth to a third child in the town, leaving the father’s name blank on the birth certificate. Shortly afterwards, she disappeared.

The facts about her in the years that followed are not easy to separate from the rumours. She narrowly escaped arrest in December 2011 over the bomb plot for which she is being sought and fellow Briton Jermaine Grant is being tried in Mombasa. Using a faked South African passport in the name Natalie Webb, she is also believed to have spent time in Johannesburg raising funds. A picture posted online shows Lewthwaite embracing Habib Ghani, a British al Shabaab fighter whom she may have married and with whom she may have had a fourth child.

Ghani, known as al-Britani, was killed this month in east Africa in an internal al Shabaab power struggle. The terror group has been keen to talk up her role, praising her as “an example to us all” and claiming she has trained an all-female terror cell. But Hansen said he believes Lewthwaite may have become a Scarlet Pimpernel figure in al Shabaab, a mythic figure whose reputation may not fully reflect her significance.

If so, he said, the enormous press speculation over her involvement could represent a propaganda victory for the terror group. “I think her operational position would be limited. But her symbolic value for al Shabaab is very large, because she’s prominent in the media and because she is a convert. She’s the daughter of a soldier who they attracted away from the western lifestyle. Her value to al Shabaab is symbolic — which should not be understated.”

By arrangement with the Guardian