Paris attacker's escape from Athens
In the weeks since the Paris attacks, a number of investigations have sought to find out if they could have been prevented.
The BBC has learnt that there was an attempt to arrest Abdelhamid Abaaoud - the ringleader of the operation - months before the attacks actually happened.
A senior anti-terrorism source in Belgium says Abaaoud was tracked to an apartment in Athens - but got away.
Chris Morris reports.
08 Dec 2015