Mina with her daughters Safaa and Rizlaine (left) and CCTV of Safaa in Vauxhall (right)

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Safaa Boular, 18, her sister Rizlaine, 22, and their mother Mina Dich, 44, aimed to unleash carnage on the streets with knives, guns, hand grenades or vehicles. In conversations bugged by police, they joked about staging a Mad Hatter’s tea party – code for a mass-casualty attack on the streets of London. Dreaming of becoming martyrs for Islamic State, they fuelled their blood lust by poring over ghastly videos of beheadings and battlefield dead. They hoarded pictures of female martyrs – women in burkas wielding assault rifles – and small children carrying guns.

They also kept images of Choudary, whose hate-filled rants have inspired a generation of jihadists including Michael Adebolajo – one of the killers of soldier Lee Rigby. A security source said: “This case shows the enduring influence of Choudary in poisoning the minds of men and women who plan and carry out acts of terrorism in this country.” Targets for the Mad Hatter attack included crowded streets around the Palace of Westminster and the British Museum. Rizlaine Boular and Dich also carried out “hostile reconnaissance” at the headquarters of MI6 on the south bank of the River Thames in London.

Mina Dich, 44, is the mother of Safaa and Rizlaine

Rizlaine and Dich also carried out ‘hostile reconnaissance’ at the headquarters of MI6

This case shows the enduring influence of Choudary in poisoning the minds of men and women who plan and carry out acts of terrorism in this country Security source

Rizlaine later practised stabbing victims with a six-inch kitchen knife, sparking fears she might be planning to attack MI6 spies outside their offices. Police bugged their conversations and Safaa was heard sneering at the victims of the Westminster Bridge attack in March last year. With mock sympathy, she said she would lay flowers at the scene. Yesterday Safaa was found guilty at the Old Bailey of preparing acts of terrorism. Her sister and mother admitted the same offence at an earlier hearing. Safaa is one of the youngest females to be charged with terror crimes. The trio will be sentenced at a later date. Khawla Barghouthi, 21, of Willesden, north-west London, admitted failing to inform the authorities about a terror plot. She will be sentenced with them. Deputy Assistant Commissioner Dean Haydon, of the Metropolitan Police, said: “All three women were filled with hate and toxic ideology and were determined to carry out a terrorist attack. Had they been successful, it could well have resulted in people being killed or seriously injured.” Rizlaine’s stabbing rehearsal at her home in Willesden was bugged by Scotland Yard and helped to prompt the decision to send in armed police. Dressed in a burka, she allegedly tried to attack one of the heavily armed marksmen and was shot four times in the stomach at close range. She survived after receiving first aid from the armed offi cers at the scene. Investigators discovered how Safaa Boular was the dominant figure in the cell.

Safaa Boular is one of the youngest females to be charged with terror crimes

Khawla Barghouthi, 21, admitted failing to inform the authorities about a terror plot

She was only 16 when she was “inspired” by coverage of the Paris massacres in November 2015, when IS killers slaughtered 130 people and wounded more than 400 in gun and bomb attacks. Safaa first wanted to travel to Syria and become a jihadi bride by marrying an IS fighter whom she met online. She and Coventry-born Naweed Hussain, 32, discussed blowing themselves up with suicide belts in the war zone, the Old Bailey heard. He fuelled her extremist views by sending her images of atrocities in Syria, including beheadings and other executions, the jury was told. Hussain also sent her £3,000 so she could travel to Syria for her wedding. But the marriage plan was thwarted when police seized her passport and Hussain was later killed in Raqqa. Safaa and her fiance never met but were sometimes in contact via the internet for up to 12 hours a day. She later claimed that she was an innocent young girl and accused the IS man of “grooming” her for sex and extremism. But Mr Haydon said: “Safaa Boular is not an innocent teenager. She is confident, articulate, intelligent and mature. “If we had not arrested her, there is no doubt she would have carried out an attack on the streets of London, causing injury and death.” The women also hoarded images of radical preachers Khalid Yasin and UK-born Muslim convert Trevor Brooks, also known as Abu Izzadeen. Normally in a full-body burka, Safaa wore Western clothes throughout her trial in an attempt to convince jurors she had spurned fundamentalism.

Coventry-born Naweed Hussain, 32, was killed in Raqqa