British Transport Police armed with 50,000 volt Tazer guns are being deployed on the Tube and London's rail network for the first time.
The force say the Tazer, which fires a barb to deliver the shock and has a range of 25 feet, will be given to 46 trained officers in response teams.
Until now only the Metropolitan Police in London and a section of the Territorial Support Group were equipped with the weapon in London. In Vancouver, a Canadian, was recently killed by a less powerful Tazer gun.
The increasing use of Tazers , first introduced in 2003, continues to cause controversy. Last year the Home Office announced plans to arm forces in England and Wales with 10,000 Tazers and train 30,000 officers to use them.
