"All of them left in a hurry one day, she was crying, she was so upset, she said that her mother had died and she had to go back to her country," the worker at the apartment complex said. "They packed their belongings and when I stopped her at the gate while checks were made that they owed no money to the landlord, she became so angry. She threatened to kill me, to cut me up in pieces."
Lewthwaite's husband, who the worker immediately identified as "Nick" from recent photographs taken after the birth of their child in South Africa, asked repeated questions about people who visited the nearby shopping centre.
"He asked me about it, whether there were Europeans, whites, who went there, whether there were a lot of Muslims who went there," the worker said. "He said he was working for Interpol in France and needed the information for an investigation. I had no reason to disbelieve him."
Four days after the family fled, officers from the Special Branch of Kenya's National Security and Intelligence Service, as it was then known, raided the apartment and questioned neighbours.
Lewthwaite did not wear Islamic clothing when she lived at the property, in Nairobi's Lavington suburb, but sometimes wore a colourful headscarf that covered her hair. It was not clear why or where the family fled in July 2011. Lewthwaite's Kenyan visa expired at the end of August.
In 2010, Lewthwaite gave birth to her fourth child, Surajah, at an upmarket private health clinic in Johannesburg where she gave a false address.
The Daily Telegraph was told this week that Surajah's father is Abdi Wahid, who defected to al-Shabaab, the Somali terror group to which Lewthwaite has also been linked.
In pictures published for the first time this week, Lewthwaite, the widow of the July 7 suicide bomber Germaine Lindsay, was shown sitting in a South African hospital bed cradling Surajah, with a man, believed to be Wahid, standing alongside. The picture was taken in the Genesis clinic, in the Johannesburg suburb of Saxonwold. It has eight private rooms with facilities more commonly found in a boutique hotel.
Her use of the clinic seems at odds with her alleged alliance to an Islamist terrorist group intent on attacking Western targets.
Lewthwaite's midwife, Lesley Rose, said the couple opted for a water birth, paid R6000 ($760), which they settled in cash, and stayed for six hours after the birth rather than the standard two nights.
Under the name Natalie Faye Webb, Lewthwaite was registered at four addresses in the Mayfair area, which is home to large Indian and African Muslim populations, with numerous mosques. But she gave the clinic an address in the bohemian suburb of Melville, which is popular with media workers and young professionals. The property's owner, who lives in Europe, said he was "outraged" that she had used his address.