In his defence, Mohammed Hamid painted himself as a bit of a Jack the Lad and some of his ranting and raving would certainly qualify him for serious psychiatric assessment.

Britain’s security services have made the mistake of dismissing such loudmouths before. In the late 1990s, MI5 and others regarded Abu Hamza al-Masri, the imam of Finsbury Park mosque, as “a harmless clown”.

The judgment made was that Abu Hamza’s vitriolic views about Jews and infidels were offensive but he was not a threat to Britain. That was an erroneous judgment and the damage eventually done to British and international security by Abu Hamza’s stewardship of Finsbury Park mosque was immense.

Hamid and Attila Ahmet were close disciples of Abu Hamza, who is now in jail, and another firebrand preacher, Abdullah el-Faisal, who has been deported to Jamaica. When Abu Hamza was jailed in 2004 they took up his mission of brainwashing and grooming recruits for holy war.

Ahmet, who called himself Abu Abdullah and was one of the Finsbury Park heavy mob, took over his mentor’s street sermons outside the closed and boarded mosque. He also assumed the role of media demon, airing his objectionable views to anyone who poked a camera in his face.

Hamid was more subtle, luring recruits through talks at Speakers’ Corner in Hyde Park and his Oxford Circus bookstall. Muktar Said Ibrahim, the leader of the 21/7 bomb cell, helped him out at the stall.

Hamid and Ahmet embarked on the same outdoor activities — designed to test and bond their tutees — that Abu Hamza had prescribed for his followers. The Jameah Islamiyah School had also been one of his haunts.

The significance of the arrest of the pair in 2006 can be measured in that it was followed by a noticeable lull in al-Qaeda activity in Britain.

Hamid, Ahmet and their associates — including the 21/7 gang — may well have been the last graduates of Abu Hamza's Finsbury Park terrorist finishing school. Their imprisonment meant that a key recruitment network had been taken out of operation.

The relative quiet of the next few months allowed Scotland Yard’s Counter-terrorism Command to take on the intricate task of investigating the murder in November 2006 of the Russian dissident Alexander Litvinenko.

It was only a pause. Al-Qaeda has proved itself to be a resilient organisation that absorbs blows, regroups and reforms its networks and returns. Striking against Britain remains one of its key objectives.

Times Recommends

• Swine flu vaccine for all as drug rushed through
• Artificial sperm and the race to build a baby
• BBC jets out stars to tout for prizes