Last year Moez Garsalloui was sentenced to eight years in prison by a Belgian appeal court. He stood trial with seven other defendants in connection with the recruitment of fighters for a Holy War.
His wife Malika El Aroud was the central figure in the case. She is the widow of the man who assassinated Ahmed Shah Massood, the Afghan opposition leader, shortly before the 9/11 attacks.
Malika El Aroud ran several radical Islamist websites and recruited fighters for a Holy War in Afghanistan. She and her husband were convicted of offences related to these websites and the recruitment of fighters, because there was insufficient evidence to convict them for involvement in terrorist attacks.
Brussels police stress that there is a difference between intelligence and being able to produce sufficient evidence to secure a conviction in court. The investigation showed that Malika El Aroud's husband entertains high level contacts in Al Qaeda.
A police source told VRT News: "In the course of the investigation we discovered several people who left for Turkey via this network. We established that these people effectively go and stay in Pakistan, in the borderlands near Afghanistan, where they are trained. We have also acquired images showing Moez Garsalloui shooting a rocket. It's clear he was no tourist."
"Many Jihad students return to Belgium and at that point it is difficult to decide what to do. Do we keep them under supervision or intervene immediately?"
Detectives decided to take action when they learnt that "students" linked to Malika El Aroud were planning to execute an operation.
The story of the Belgian branch of Al Qaeda is told in "Osama's Curse" that is broadcast on Canvas at 9:10 CET on Monday.