Operation Spanner was the name of an operation carried out by police in the United Kingdom city of Manchester in 1987, as a result of which a group of homosexual men were convicted of assault occasioning actual bodily harm for their involvement in consensual sadomasochism over a ten-year period.
The resulting House of Lords case (R v Brown, colloquially known as "the Spanner case") ruled that consent was not a valid legal defence for wounding and actual bodily harm in the UK, except as a foreseeable incident of a lawful activity in which the person injured was participating, e.g. surgery.
Legal reform and review of the concern is ongoing and the convictions are controversial due to issues of whether a government or one's self is justified to control one's own body in private situations where the only harm is to consenting adults.
The police had obtained a video which they believed depicted acts of sadistic torture, and they launched a murder investigation, convinced that the people in the video were being tortured before being killed. This resulted in raids on a number of properties, and a number of arrests.
The apparent "victims" were alive and well, and soon told the police that they were participating in private BDSM activities. Although all of those seen in the videos stated that they were willing participants in the activities, the police and Crown Prosecution Service insisted on pressing charges. Sixteen men were charged with various offences, including assault occasioning actual bodily harm.