Michael Adeboloja is reportedly one of the London attackers. He allegedly answers to his Muslim name "Mujahid," or "one who fights Jihad." He is reportedly the man in the video alone. Word is that he is a Muslim convert.
Someone claiming to be his friend has identified him on Twitter. His nationality is still not known, but it may be Somali. There are not many things on Google about the man, who has not been officially identified by the police. Reports and video show him bragging over the murder, praising God for the death of an alleged British soldier.
UPDATE: Photo here.