The attacks on New York and Washington on 11 September, 2001 made the world take a close look at existing anti-terrorism measures.
Security services in Europe found they had a problem on their hands.
One of the first steps the EU took was to establish a definition of terrorist crimes and minimum sentences they should carry.
Moroccan Mounir al-Motassadeq was the first to go on trial in Europe in connection with the US attacks.
He is being re-tried after his initial conviction was overturned.
Meanwhile not all EU states have applied the minimum sentences.
Italy has not even adopted the much-vaunted European arrest warrant.
In the wake of the attacks on the US, President Bush made a grand announcement that he would “freeze terrorists’ funding.”
Europe was quick to follow, setting up a terrorist list of individuals and organisations whose assets were to be frozen. The list is regularly updated.
Then came the train attacks in Madrid. Europol reactivated its counter-terrorist force, and the EU brought in its first anti-terrorism co-ordinator. Among a raft of leglislation, there are currently plans to make operators keep phone and electronic communications for a minumum of a year.
The financial sphere has seen perhaps the most EU-wide cooperation.
The amount of money that has to be declared if being taken across borders has been reduced to 10,000 euros, while measures against money-laundering are also underway.
On top of its bodies for police and justice, the EU will, from this May, have an agency for managing borders.
But the EU’s anti-terrorism co-ordinator Gijs de Vries says coordination between the police and judiciary is still poor. He also says that the EU needs a common evidence warrant.
Experts say the Madrid bombing suspects, who were living in Spain, did not rely significantly on foreign logistical support.
Britain, as EU president later this year, will lead the drive to stop potential terrorists becoming radicalised within member states.