Jewish security chiefs cautiously welcomed the news this week that extremist preacher Anjem Choudary will serve time behind bars for “inviting support” for terrorist group Islamic State.

British-born Choudary, 49, a lawyer and leader of the banned al-Muhajiroun group, was convicted for activities in 2014-15, together with co-defendant Mohammed Mizanur Rahman.

While both men are yet to be sentenced, they could face up to ten years in jail, after being found guilty of drumming up support for IS among tens of thousands of followers, dozens of whom have gone on to commit terrorist atrocities.

Writing in Jewish News, Community Security Trust director Mark Gardner acknowledged that Choudary, who inspired the man who bombed Mike’s Place in Tel Aviv in 2003, was “a very clever man” who “danced on the edge of the law” for years, but – while welcoming the verdict – suggested its timing might represent a deteriorating security situation in the UK.

“It is hard to shake the suspicion that he has only now been convicted, because the danger he has posed in recent months or years, demonstrably outweighs whatever intelligence benefits were believed to be being gained by letting him stay at large,” said Gardner. “If so, this would be very worrying, because it would be a sign that the danger posed here and now by British Jihadists has never been higher.”

Choudary has long called for Sharia law in Britain, and even suggested that Buckingham Palace should be turned into a mosque, but it has been his comments on Israel that has concerned the Jewish community.

As recently as May this year, he said: “As far as Muslims are concerned, we want the whole of Palestine, which includes what Israel currently occupies, liberated.”

Referring to controversial comments from Naz Shah MP, which she subsequently acknowledged were anti-Semitic, he said: “We would prefer… those who came to occupy the Muslim land of Palestine should be returned from where they came. They are free to live in Russia and Poland and other places.”

Sue Hemming from the Crown Prosecution Service said Choudary and Rahman “knowingly sought to legitimise a terrorist organisation and encouraged others to support it”. She added: “They used the power of social media to attempt to influence those who are susceptible to these types of messages, which might include the young or vulnerable.”

Among Choudary’s past supporters was Omar Khan Sherif, a 27-year old suicide bomber from Derby, who attacked Mike’s Place, a pub in Tel Aviv, in April 2003.

Sherif fled after his 21 year old accomplice, Hounslow resident Asif Hanif, blew himself up at the bar, killing three people and injuring 60. Sherif’s body was discovered on a beach two weeks later, and identified by DNA samples. An al-Muhajiroun spokesman in Derby at the time suggested Sherif had been tortured and killed by Israeli security services.

Commenting on Choudary and Rahman’s guilty verdicts announced this week, Commander Dean Haydon of Scotland Yard’s counter terrorism command said: “These men have stayed just within the law for many years, but there is no one within the counter terrorism world that has any doubts of the influence that they have had, the hate they have spread and the people that they have encouraged to join terrorist organisations.”

Haydon’s team trawled through 20 years’ of Choudary and Rahman’s communications in the run-up to the prosecution, including their July 2014 Skype call to Mohammed Fachry, a man convicted of recruiting for the Islamic State in Indonesia, in which they pledged their allegiance to the Islamic State’s leader, Abu Bakr al-Baghdadi. The oath, signed by Choudary, was then published by Fachry on an Indonesian website.

In 2010, then Home Secretary Alan Johnson banned al-Muhajiroun, a radical Islamist group glorifying suicide bombers and preaching anti-Semitism, in a move welcomed by the Jewish community at the time, but Choudary has remained free. He will be sentenced on 6 September.