< ! -- WP : NFCC violation : The " ring of steel " measures were introduced by Owen Kelly , then the City of London Police commissioner , following the Provisional 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 . The " Traffic and Environmental Zone " was officially established in 1993
1993 Bishopsgate
1993 Bishopsgate bombing
Traffic and Environmental Zone