The ring of steel is the popular name for the security and surveillance cordon surrounding the City of London, installed to combat IRA and other terrorist threats. Roads entering the city are narrowed and have small chicanes to force drivers to slow down and be recorded by CCTV cameras. These roads typically have a paved strip down the middle with a sentry box where police can stand guard and monitor traffic. Some roads have been closed to traffic entirely. Despite the term "ring of steel", the roadblocks and chicanes are actually created with concrete blocks, sometimes plastic coated, that are wedged together.
The measures were introduced following massive IRA bombs in the City in the early 1990s (see for example the Baltic Exchange bombing).
June 13, 2006
NYPD Not Wedded to Downtown Ring of Steel
Police Commissioner Ray Kelly said that the drop in Homeland Security funding means a "cessation of the Lower Manhattan Security Initiative" - aka the "Ring of Steel" for the Financial District. A few months ago, the NYPD proposed an ambitious plan to install license plate readers and vehicle barriers downtown to tighten up security, modeled after what London did after its early 1990s bombings.