Mr. Smith introduced himself as 'Major Tony Smith' however upon typing his username into a server he gave his name as 'A.D Smith' so his real name could be either.
Mr. Smith was assigned to investigate the aftermath of The Biogenetic Research Centre by collecting evidence such as the CCTV tapes. Upon entering however he comes face to face with the Headmaster who had returned as a clone of his former self. After a heated discussion on how he could be in the locked building, the Headmaster hypnotised Mr. Smith and uses him as his right hand man.
Smith turns out to be resourceful and leads the Headmaster to the green hand badges technology using his status as a Major. He also made a good babysitter for Tim Dexter and his assistant when their brains got wiped from using Direct-brain access and effectively turned them to infants. It isnt known what happened to Mr. Smith after the events of The 'The Demon Headmaster Takes Over' he probably went back to his high rank job and had no recollection of what happened.