This week public debate constantly swirled around ghosts.

They ranged from the ghost of the deposed King Constantine, whose death reawakened old divisions, to the ghost of the far right, which seeks once again to rear its ugly head if the political system does not find a constitutional formula to block it.

The arrest on charges of an armed robbery in Patras of the son of a convicted member of the now defunct 17 November terrorist group reminded us that there is yet another ghost.

Terrorism may be seeking a way to come out of the shadows in a crisis period when public attention is focused on other matters.

The officers of the counter-terrorism bureau who are closely scrutinising the Patras case do not believe that the robbery was an effort to fund a new terrorist group that is seeking to establish itself.

Yet, the investigation is necessary and must be exhaustive, as the victory over terrorism is never final.

It has been 20 years since the rooting out of 17 November ended the last serious threat.

What one saw thereafter were efforts to revive terrorism that had victims but did not endure in the long run.

One way or another, despite mistakes or delays, the Greek state proved to be better prepared and Greek society rejected terrorism. In the past these things could not always be taken for granted.

We must always remember our duty to display constant vigilance in order to deter the creation of new terrorist cells, without waiting for events that receive news coverage to ring the alarm bells.