London attacks: Italy's 'clear conscience' over Zaghba
The chief of Italian police has said he has a "clear conscience" over the actions his force took regarding Youssef Zaghba, one of the London Bridge attackers.
But Franco Gabrielli also said he understood the "difficulties experienced by people who are working in a very complex situation".
Zaghba, 22, a Moroccan Italian who lived in East London, was detained on suspicion of terrorism offences in Italy last year after police at Bologna Airport thought he was attempting to travel to Syria.
Material relating to the so-called Islamic State group was found on his phone.
He was not prosecuted, but the Italian authorities said they told UK intelligence agencies about him and added his details to an EU-wide database, the Schengen Information System 2 (SIS 2).
It's thought the main purpose of including Zaghba on the SIS 2 database was to track his movements, should he leave Italy and travel elsewhere in Europe.
The Home Office is not commenting on Zaghba's case.
Zaghba carried out the attack on Saturday along with Khuram Butt, 27, and Rachid Redouane, 30, who both lived in Barking.
Eight people were killed and 48 injured when the van they were driving hit pedestrians on London Bridge, before the three got out and stabbed people in nearby Borough Market.
SIS 2 is designed to trigger an alert when a suspect passes through passport control.
Border officers and/or police can then make inquiries, for example, to find out their reasons for travel and where they're going.
That information can then be passed back to the original country. It is also possible for the information to be shared with security officials in the destination country.
The fact an individual is on SIS 2 does not mean they can be automatically arrested or stopped. The action that can be taken depends on the type of alert on the system.
No-one has confirmed exactly what happened when Zaghba arrived in the UK earlier this year.
But it is likely that he was subject to a check under what's known as "Article 36" with the aim of gathering intelligence about his movements, rather than stopping him from entering the UK.
The College of Policing, which sets guidelines for police in England and Wales, has a guide on the use of SIS 2.
It says: "Article 36 allows a SIS 2 state to place an alert on a person, vehicle or container requesting that if the person or object is located, either a discreet check or a specified action is taken.
"An Article 36 alert can be raised for the purposes of prosecuting criminal offences (36(2)) and for preventing threats to public security (36(3)).
"Requests for specific action relate to matters such as searches. Searches cannot be conducted (using SISII alone) in the UK as this would be contrary to the Police and Criminal Evidence Act 1984.
"Under UK law, the only action officers can take is a discreet check."
In terms of terrorism suspects, it says countries "can issue an alert...for those they believe are involved in terrorism related activity".
It says: "The EU is actively encouraging the use of this alert to combat the foreign fighter phenomenon.
"The alert can be used for those seeking to travel to other states to participate in terrorist activity or who are supporting the activity, through delivering funds, for example.
"The alert can also be used to track individuals who are at risk and are seeking to travel to another state because of political ideology."
When an Article 36 alert is triggered "officers should discreetly collect as much information as possible" unless an "immediate response alert" is issued in which case an "immediate" response is called for.
The UK has other databases at the border - including the UK Warnings Index, which contains a list of wanted people and criminals.
No one has confirmed whether or not Zaghba was on this Index, but it's thought to be very unlikely.
Border officials also have the power to stop non-UK nationals from entering Britain on national security grounds - but the threshold for doing so in relation to EU citizens is quite high.