 the ring of steel is the popular name for the security and surveillance cordon including of a large number of cctv cameras surrounding the city of london, installed in the 1990s to deter the provisional ira and other threats.city of london police. "3.2.4 the automated number plate recognition (anpr) system and the corporation of londonâs traffic and environment zone culminate in what is generally referred to and known as the âring of steelâ.bbc news (2003-12-08) the term was borrowed from an earlier stage of the troubles when the centre of belfast was fortified against attacks; this fortified perimeter was known as the "ring of steel".coaffee (2004), p. 201 (pdf p. 2) first paragraph. == recent use == thumb|right|one of the checkpoints in july 2014 when it wasn't being actively used. the road narrowing and slowing of traffic are clearly seen following the september 11 attacks in the united states in 2001, and a reported increased terrorist threat to the united kingdom, security was stepped up with occasional spot checks on vehicles entering the cordon, although not to previous levels. in december 2003, the ring of steel was widened to include more businesses in the city. this was as a direct result of a police report that categorised a terrorist attack on the city as "inevitable". traffic entering the city is also monitored and recorded at the boundary of the london congestion charging zone, which covers a wider area. ==history and purpose== the measures were introduced by owen kelly, then the city of london police commissioner, following the ira bombing campaign in london in the 1980s and early 1990s including attacks within the city such as the 1992 baltic exchange and 1993 bishopsgate attacks. roads entering the city were narrowed and small chicanes were created to force drivers to slow down and be recorded by cctv cameras. these roads typically had a concrete median with a sentry box where police could stand guard and monitor traffic. city planners call these types of precautions "fortress urbanism".lipton (2005-07-24) some roads were closed to traffic entirely.coaffee, jon (2003) p.176 despite the term "ri
City_of_London Defence_of_London Infrastructure_in_London Surveillance