He did not know that one of the people he was conversing with was an undercover police officer, telling her: “We will, with the help of tawhid [the belief in the oneness of God], raise the black flag over London.”
Anderson was originally sentenced to three years’ imprisonment in 2016 for promoting Isis outside Topshop in London’s Oxford Street.
It later emerged that he had gone to the same Luton gym as the Westminster attacker, Khalid Masood, and an Isis fighter who was killed in a drone strike.
Following his release from prison, he was subjected to terrorist notification requirements, which are intended to enable police to monitor convicts and manage any risk they pose.
But he was able to commit a string of terror offences through summer and autumn last year.
Anderson was handed a seven-year jail sentence at the Old Bailey on Wednesday, after admitting 15 terror offences.
Judge Philip Katz QC said some of the material shared by Anderson was “at the worst end of the range seen in this court”.
“Like so many others, you were spending too much time in the dark regions of the internet [during the coronavirus lockdown],” he told the defendant.
Patrick Harte, defending, said his client had expressed remorse after turning “to the internet for some sort of release” during the pandemic.
Earlier this year, Anderson pleaded guilty to 10 counts of disseminating terrorist publications on Facebook and Telegram. They included official Isis propaganda films showing execution and beheadings, calling for terror attacks and glorifying suicide bombings.
He admitted a further four charges of possessing terrorist publications, relating to issues of Isis’ official Rumiyah magazine, including editions containing instructions on knife and vehicle attacks.
Anderson also pleaded guilty to breaching terrorist notification requirements by not giving police details of current email accounts.
Mr Harte previously told the Old Bailey that Anderson admitted dissemination “on a reckless basis in the sense he did not intend his act to encourage terrorism”.
Anderson is one of numerous terror convicts linked to Anjem Choudary’s banned al-Muhajiroun network.
Concerns had been publicly raised about his online activity before the period covered by the case.
In 2019, The Sun reported that he had shared hateful images on his Facebook page including one showing an AK-47 assault rifle laid in front of a prayer mat.
The caption said: “Remember the Mujahideen [warriors] in your prayers because they are fighting on your behalf.”
Anderson, a former mechanic with five children, has previous convictions for assault and possession of an imitation firearm.
Born as Andrew Anderson, he converted to Islam while serving a jail sentence for robbery in the 1990s.
He later became known for preaching from stalls linked to al-Muhajiroun.
In August 2014, he was spotted on Oxford Street handing out a leaflet on the Isis “caliphate” and challenged by two Muslim women who reported him to police.
Photos of the leaflets circulated on social media showed them declaring the “dawn of a new era” and calling on Muslims to pledge allegiance and migrate to the new so-called Islamic State.
The case resulted in his prosecution for inviting support for Isis, which was the same offence used against al-Muhajiroun leaders Choudary and Mizanur Rahman.
Despite being hailed as the UK’s “most dangerous Islamist group” and banned as a terrorist organisation since 2006, no one has ever been successfully prosecuted for membership of al-Muhajiroun itself.
Additional reporting by PA
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