The names of two of the four people believed to have taken part in last week’sbotched bombings in London have been made public in an bid to speed up the investigation.They are Muktar Said-Ibrahim, also known as Muktar Mohammed-Said, and Yasin Hassan Omar. Police have arrested two more people in connection with the failed attacks. Officers also raided an address in north London but nobody was detained. While normality appears to have returned to the underground stations hit by the deadly attacks of July 7, authorities say they are in a race against the clockas the suicide bombers are thought to be still in Britain and perhaps preparing to strike again. The investigation has been tainted by the shooting of a Brazilian electrician whom police mistakenly thought was on the verge of carrying out a suicide attack.