Police have confirmed that the matter has been referred to the Independent Police Complaints Commission.
It is understood this relates to the fact that police were in pursuit of a car before the fatal collision.
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"We are not afraid." Those were the defiant words of the Prime Minister this morning as she addressed the Commons.
Andreea Cristea, 29, remains in a critical condition after being rescued from the Thames after a terror attack along Westminster Bridge.
The Prime Minister has praised the former soldier's "huge professionalism" in trying to save the life of Pc Keith Palmer.