Just over a week after terror struck the heart of London, police investigators have found nothing to link terrorist Khalid Masood to extremist groups.
The day after the attack occurred near the UK parliament, Prime Minister Theresa May said the 52-year-old had come to the attention of spy agency MI5 as a peripheral figure in an investigation into violent extremists.
But sources familiar with the inquiry have rejected those fears. They said he had appeared on MI5's radar when they were looking into "multiple plots" in Luton, a town 55 km north of London, where he was living about five years ago.
Masood's name came up in a probe into a network suspected of helping people travel from Britain to jihadi groups in Afghanistan and Pakistan, a European government source said, but nothing they have found ties him to any group, faction or known radical preachers.
Instead, investigators suspect it was reading and watching extremist material online that led him to plough a rented car into pedestrians on London's Westminster Bridge, killing three people before he charged into the walled grounds of parliament and stabbing a policeman to death.
He was shot dead after an attack that lasted 82 seconds.
"I have no evidence he discussed this with others. Whilst I have found no evidence of an association with Islamic State or al-Qaeda, there is clearly an interest in jihad," said Neil Basu, senior national coordinator for UK counter-terrorism policing.
The police investigation also strongly points to Masood being a lone wolf, carrying out the kind of attack Islamic State spokesman Abu Mohammed al Adnani called for when the group was at the peak of its power in late 2014.
Since last Wednesday, police have arrested 12 people close to Masood in connection with the attack. One remains in custody and all but one of the others have been told they face no further action.
"Whilst we believe at this stage Masood acted alone in his execution of the attack, our investigation continues to establish whether there are any others involved in any way and I do emphasise this is a live investigation," Craig Mackey, acting head of London police, said.
When and how he became radicalised is now the main focus of the investigation.
Senior counter-terrorism figures have warned in the past that some people had become radicalised in just weeks via material they accessed over the internet.