The incident is being investigated by the Counter Terrorism Command.
The Telegraph said Mr Mohammed Mahmoud was believed to be the man heard shouting "Don't touch him!"
"I hit him on his stomach. and then me and the other guys. we held him to the ground until he couldnt move".
"Extra police resources have already been deployed to reassure communities, and police will continue to assess the security needs of mosques and provide any additional resources needed", she said.
"Our thoughts and prayers are with all affected by these violent and reprehensible attacks".
Police said the man who was being given first aid at the scene before the vehicle was driven into pedestrians had died but it was not clear whether his death was directly linked.
Though Trump was quick to denounce those earlier attacks, on Monday morning-with the targets and victims Muslim and the alleged assailant a white male-the president found better things to do with his Twitter account.
Numerous victims are believed to have just left evening prayers at a Muslim Welfare House after breaking the Ramadan fast.
People at the scene in north London where one man died and ten were injured described how he allegedly shouted "I'm going to kill all Muslims - I did my bit" after ploughing into the crowd gathered on the pavement.
Police have arrested the 48-year-old driver of the van who ploughed into a crowd of pedestrians in north London, next to a Muslim center and close to a mosque.
At least one person was killed and 10 others were injured in the assault, which authorities were treating as a terrorist attack.
"The time, he was planning for it, the target, he was planning for it, and the place - outside a mosque".
Several people were injured in north London early on Monday when a van rammed into worshippers leaving a mosque, witnesses said, in what British police described as a "major incident".
So, it's the holy month of Ramadan.
Manchester was hit by a deadly attack on May 22 when a suicide bomber killed 22 people at an Ariana Grande concert.
Police said all the casualties were Muslims.
Mahmoud said he was in the mosque shortly after prayers when "a brother came in, quite panicked, and said that somebody had run over a group of people and tried to kill them so we rushed out". He was taken to the hospital as a precaution.
"My message to the Government is - we need to get the right of level of funding for a capital city", Khan said in a news conference.