London terrorist was British citizen investigated by MI5, PM May reveals

British Prime Minister Theresa May revealed Thursday what appears to be a blunder by her country's intelligence services. She said the terrorist who perpetrated the attack in London the previous day was a British national who had been investigated by MI5, the country's domestic intelligence service, on suspicion of Muslim extremism and links to terror. May also stated during the BBC interview that the terrorist acted alone.
DEBKAfile's intelligence sources report that it is too early to conclude that the terrorist carried out the attack by himself, and that such a conclusion by the British authorities indicates their desire to portray the incident as an act of an individual even as the expansion of the investigation, including arrests made overnight, shows concern that the terrorist was just a small part of a extensive terror network.