Any action under this Convention is time-barred if judicial or arbitral proceedings have not been instituted within a period of two years.

If a crime took place several years ago, notes Ms Powell, a Greek court may regard it as time-barred and decline to extradite, even though other EU countries would count it as still prosecutable.

Other real-time systems use algorithms to detect suspicious behaviour, such as a group loitering near a door where entry is barred, or to spot items of luggage that seem to have been left unattended.