It's thought the 22-year-old Manchester suicide bomber had help.
Salman Abedi died when he set off the bomb at the Ariana Grande concert in Manchester.
Counter terrorism expert Will Geddes told Mike Hosking a considerable amount of work is required to create the device used.
"This was a pretty sophisticated plot, and this wasn't a lone individual that simply decided on a spontaneous whim to carry out an attack."
Geddes said the attacker was known to authorities, but was not considered high risk.
He said individuals can be on the radar, but authorities have a constant challenge as to who they can prioritise with the finite resources they have available.
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