One of six people arrested in a counter-terrorism operation in London on Thursday was once suspected of trying to travel to Syria to join so-called Islamic State, it has emerged.
Mohamed Amoudi, 21, was deported to the UK from Turkey in 2015, but released without charge.
Police said they foiled an active terror plot when they raided a house in Willesden, north-west London.
A 21-year-old woman who was shot during the operation remains in hospital.
Mr Amoudi was arrested on Thursday after the raid in Harlesden Road - the house had been under observation by police.
It has now emerged that he had travelled with two 17-year-old boys to Turkey, and they were believed to be heading for Syria.
They were sent back to the UK and all three were released without charge after being questioned by British authorities.
A 20-year-old woman, a 16-year-old boy, and a man and woman both aged 28 were also arrested, as well as a 43-year-old woman, who was arrested at another raid in Kent.
All of them were detained on suspicion of the commission, preparation and instigation of terrorist acts.
The woman who was shot is under police guard in hospital but has not been arrested "due to her condition".
It is believed to be the first time a woman has been shot by police in 10 years. The last time was in 2007 when Ann Sanderson was fatally shot in Kent.
The Willesden raid has been referred to the Independent Police Complaints Commission and the Met's directorate of professional standards, as is procedure.
The IPCC said it was gathering evidence but that no officers were under investigation.
A neighbour living close to the raided property told the BBC she had reported its residents to authorities on several occasions, for anti-social behaviour.
She claimed there was often noise throughout the night, including the sound of prayer, and that on several occasions she had reported the residents to the police and local authorities over the noise.
During one incident, the neighbour claimed, she was verbally abused and her door was kicked.
A cleaning company was run from the property, the neighbour said.
On Thursday, police also arrested a 27-year-old man at the junction of Parliament Street and Parliament Square, in London, as part of an intelligence-led operation.
He was identified on Friday as Khalid Mohamed Omar Ali, a British national who is believed to have gone to school in Tottenham, north London, but was not born in the UK.
The Met said he had been detained on suspicion of terrorism offences and that knives were recovered from the scene.
It has now emerged that he had spent some time in Afghanistan and returned to the UK at the end of last year.
He had been on the force's radar for some time and it is thought police acted after a concerned family member contacted them.
The Metropolitan Police said the two counter-terrorism operations were not linked.
Neil Basu, deputy assistant commissioner, said that in both cases he believed "we have contained the threats that they pose".