Until a key arrest barely three weeks ago, not a single member of the shadowy Greek terror group, November 17, had ever been captured.

For 27 years, the left-wing militant organisation carried out a string of bombings and shootings, killing 23 people until a near-fatal blunder which gave police their first lead.

The arrest of Savvas Xiros was a vital breakthrough

On 29 June, icon painter Savvas Xiros was captured after being seriously injured when the bomb he was apparently attempting to plant in Athens exploded prematurely.

A gun discovered nearby was found to be the same one taken from a policeman killed during a 1984 robbery attributed to November 17.

This was the first opportunity police had ever had to question an apparent November 17 member.

Vital find

Information gleaned from Xiros' interrogation led police to two arms caches filled with anti-tank missiles, automatic rifles and disguises.

Alexandros Giotopoulos: Believed to be N17's 'spiritual leader'

Among the weapons was the gun used to kill British diplomat Stephen Saunders in June 2000.

Savvas Xiros' brother Vasilis, who was arrested on Thursday, has admitted the murder of Brigadier Saunders and the 1997 killing of Anglo-Greek businessman Constantinos Peratikos.

A third brother, Christodoulos Xiros, has also been detained.

However the biggest break came when fingerprints taken from the raided arms stores were matched to 58-year-old economist Alexandros Giotopoulos. His prints had been on police records since a conviction in the 1970s.

Police had long suspected Mr Giotopoulos of having some connection with November 17, but had never had enough evidence to arrest or charge him.

Dramatic arrest

On Wednesday, Greek special forces using a fire-fighting helicopter flew to the island of Lipsi and arrested Mr Giotopoulos as he tried to make an escape on a hydrofoil.

Communist imagery dominates November 17 regalia

Investigators say that he closely matches a profile developed over the years of a man codenamed Lambros, who they believe to be the organisation's founder.

The inquiry is now focusing on possible links between November 17 and left-wing Greek dissidents, many of whom were exiled to France during the period of military rule in Greece from 1967-74.

Mr Giotopoulos - who had been using the alias Michalis Economou - is alleged to have had connections with Paris-based exiles during this time.

Observers say the high-profile murder of Brigadier Saunders - and subsequent involvement of British police in the investigation - was a significant factor in cracking November 17.

Gaining momentum

Immediately after the shooting of Mr Saunders, three officers went to Athens to assist Greek police, and others have visited the country at intervals over the last two years.

Specialist anti-terrorist officers have offered advice on the proper collection of evidence from crime scenes, cataloguing of forensic evidence and use of public appeals for information.

The operation gained further momentum after the 11 September terrorist attacks in New York and Washington, which brought a declaration from the United States that it would pursue a global campaign against all terror groups.