The man arrested on impression of fright offences after a car disintegrated outside the Houses of Parliament has been reputation as Salih Khater by government sources.
The 29 -year-old British citizen, originally from Sudan, has also been arrested on distrust of attempted murder, Met Police said.
He came to the UK as the status of refugees and was granted asylum, the BBC understands.
His brother described him as a “normal person” with no fanatical ideas and no links to any religion radical.
Abdullah Khater also said his family – who are initially from Darfur in Sudan – were in “a state of shock”.