The Manchester Arena suicide bomber had been in Malta three years before he killed 22 people at a music concert.
Salman Abedi was 19 when he was rescued from the civil war in Libya by the Royal Navy and brought to Malta.
He boarded HMS Enterprise in Tripoli in August 2014 with his British-born younger brother Hashem.
The ship brought them to Valletta’s Grand Harbour two days later, according to sources at the Ministry of Defence in London.
After being dropped off in Malta, Salman and his 21-year-old brother flew from Luqa to Manchester, where their parents were living at the time.
In May last year, he murdered 22 people – including seven children – at an Ariana Grande concert with a homemade suicide vest.
A British Government source told the Daily Mail: ‘For this man to commit such an atrocity on UK soil after we rescued him from Libya was an act of utter betrayal.’
The bomber’s brother Hashem Abedi is being held in prison in Libya by a militia group, but the English courts have requested his extradition to face trial for his involvement in the Manchester attack.
The request has so far been refused.