The most glaring slip-up was the failure to flag up the arrest of a Montenegrin suspect in Bavaria 10 days ago in a car packed with Kalashnikovs and grenades – with Paris in his sat-nav. The information was passed to Interpol but a report said the French did not seem to be interested. One of the killers, Omar Ismail Mostefai, was a Parisian who had been on a terrorist list for five years.

The petty criminal with eight convictions is thought to have travelled to Syria in the past two years. The discovery of a Syrian passport belonging to one of the terrorists suggests one or two of them might have entered Europe as part of the wave of Middle East refugees.