The killer of headmaster Philip Lawrence has been recalled to prison after he was arrested on suspicion of robbery, a probation boss said.
Learco Chindamo walked free from jail in July, 15 years after knifing the teacher to death at the gates of St George's Roman Catholic School in Maida Vale, west London.
Chindamo, 30, was arrested in the early hours of Wednesday on suspicion of robbing a man on Saturday November 13 in Belmont Street, north London.
Harry Fletcher, assistant general secretary of Napo, the probation trade union, said the murderer was recalled to custody for his own and the public's safety. He said: "Anybody who is arrested in connection with a serious offence, consideration would be given to recalling them to custody."
Detectives are continuing to investigate the alleged robbery. If Chindamo is charged, he will go before the courts and, if he denies the offence, he will stand trial.
Mr Fletcher said if Chindamo is not charged, probation staff could argue to keep him behind bars for possibly breaching the conditions of his release on licence. If that did happen, Chindamo would be entitled to a hearing before the Parole Board within 28 days. At that hearing he could try to overturn his return to prison.
Mr Fletcher said: "Before his release, he was turned down for parole at least once on the grounds he hadn't made sufficient progress. Upon release, he was placed in a probation hostel. These days there are 2,500 places in 100 hostels in England and Wales, primarily for sex offenders and people convicted of violence offences, including lifers."
Chindamo remained in a hostel until a month ago, when probation officers agreed he could live with his mother in north London.
On his release from jail, Chindamo caused outrage when a judge ruled he could not be deported to his native Italy because it would breach his human rights as he has spent most of his life in Britain.
Father-of-four Mr Lawrence, 48, was knifed and fatally wounded after going to help a pupil who was being attacked by a gang. Among the attackers was Chindamo, then 15, who went on to brag about the killing hours later. He was convicted of the murder in October 1996, jailed indefinitely and ordered to serve a minimum of 12 years.