The Edgley Optica was a British fixed-wing aircraft built for observation use and was used by the Hampshire Constabulary as an alternative to rotary-wing aircraft. The Britten-Norman Defender is used by the Greater Manchester Police, the Police Service of Northern Ireland and the Garda Síochána. The FBI deployed one Britten-Norman Defender for electronic aerial surveillance at the Branch Davidian compound during the Waco siege in 1993. In Greater London, the Metropolitan Police Service has, for a number of years, reportedly been secretly using Cessna aircraft that have been fitted with surveillance equipment capable of intercepting mobile telephone calls and listening in on conversations.