People gather in Potters Field Park during an event for the victims of Saturday nights attacks, London, June 5, 2017. [Photo/Agencies]

One of Butt's neighbours, Ikenna Chigbo, told Reuters he had chatted with Butt - also known as "Abz" - just hours before the attack on Saturday and said he appeared "almost euphoric".

"He was very sociable, seemed like an ordinary family man. He would always bring his kid out into the lobby".

Another neighbour, Michael Mimbo, told Reuters that Butt supported the north London football team Arsenal. One of the dead attackers has been pictured wearing an Arsenal shirt.

Mimbo said Butt had grown a longer beard and worn traditional Islamic dress more often over the two years he had known him, but showed no sign of radicalisation.

"As an individual he was a cool, calm guy. One of my friends would let Abz babysit his daughter," Mimbo said.

Police said on Monday they had released all 12 people arrested in the neighbourhood on Sunday without charge. However, police were investigating what appeared to be Molotov cocktails in the back of the van, Sky News reported.

Reuters