Rachid Redouane, one of three men involved in the weekend Isis attack in London, was completely unknown to security sources in the UK and Ireland.
He had married his British wife in Ireland in 2012 and lived for a time in Rathmines, south Dublin.
While he left Dublin with his wife and had been living in Barking, east London, he returned to Ireland for periods; the first such visit about 18 months ago. His wife had given birth to their child at about that time.
She never converted to Islam. She was arrested early on Sunday in the aftermath of the terror attacks. She is a care worker who had been living in sheltered accommodation in London Scotland Yard said all 12 people arrested were released without charge on Monday night. There is no suggestion of wrongdoing on her part.
The couple separated at about the time their child was born and Redouane, a pastry chef, left London for Dublin for a time.
No red flags
Redouane went back and forth between Ireland and the UK after the break-up and may have been in Ireland as recently as March, though details of his travels are unclear. His trips in and out of the country raised no red flags, prompted no surveillance or any collating of his movements. On the spectrum of security risk, he simply did not exist.
But on Saturday night the 30-year-old, who was of north African origin and had an address in east London, embarked with two other men on a killing spree, since claimed by Isis. They crashed their van into a shopfront near London Bridge and took to the streets by foot with long bladed weapons.
The three attackers fatally stabbed seven people and injured 48 others in the eight minutes before armed police shot them dead.
As well as Redouane, another one of the three men was named by British police on Monday night: Khuram Shazad Butt, also from Barking in east London.
Butt (27) was born in Pakistan but was a British citizen. While he was known to the police and MI5, there was no intelligence suggesting an attack was being planned.
Redouane claimed at different times to be from Morocco and Libya. In the follow-up operation after Saturday's attack, the London Metropolitan Police discovered documentation that showed Redouane, who also used the name Rachid Elkhdar, had lived in Ireland.
Redouane’s circumstances give rise to the obvious concern that he was radicalised and preparing to carry out a terrorist strike at a time when travelling freely between the UK and Ireland unnoticed by law enforcement.
However, sources stressed a full picture of the last years of his life must be gathered before any security lapses are identified. His death does nothing to lessen the intensity of the investigation that must now be conducted into his life in Ireland.
His reasons for initially coming to Ireland, and indeed why he returned in the last 18 months, must be established. A network of his associates in Dublin must also be determined to establish if any of them facilitated his radicalisation or his role in the atrocity.
It will be crucial to determine exactly when, where and how he was radicalised. It is only when more is known about the process that it will become clear whether the security failure was in Britain or Ireland.