Sidney Charles Cooke was born on April 18, 1927, in Stroud, Gloucestershire, England. He grew up in a rural setting and started working as a farm laborer at a young age. This early work provided him with the skills related to farm life, but it also meant he was used to the hard labor that came with it.

As he grew older, Cooke transitioned to working as a fairground worker. This job allowed him to travel around the United Kingdom easily, which gave him the opportunity to meet different people and move from place to place. Being a fairground worker also involved setting up and operating amusement rides, including a child's version of the high striker, a game that requires strength to hit a target and ring a bell.

In November 1985, Sidney Cooke led a group that gang-raped 14-year-old Jason Swift. After the incident, Jason was killed, and his body was discovered in a shallow grave by a dog walker. The Metropolitan Police conducted an investigation that led to Cooke's arrest along with three other men: Leslie Bailey, Robert Oliver, and Steven Barrell. Initially charged with murder, Cooke and the others were convicted of manslaughter, and on May 12, 1989, Cooke was sentenced to nineteen years in prison.

On June 1, 1984, Cooke was also implicated in the murder of seven-year-old Mark Tildesley. According to Leslie Bailey, Cooke lured Tildesley away from a funfair. Although Bailey confessed to the murder, the Crown Prosecution Service decided not to charge Cooke, as he was already serving time for the manslaughter of Swift. Over time, Cooke's role in Tildesley’s murder became a subject of further investigation but was not acted upon until years later.

Cooke is also suspected of being involved in the murder of six-year-old Barry Lewis, who went missing while playing with friends in September 1985. His body was discovered in April 1986. During police investigations, Bailey confessed that Cooke’s gang had abducted, drugged, and raped Lewis. Bailey provided details about the murder, leading authorities to Lewis's burial site. Although Bailey was the only one convicted, police viewed Cooke as the ringleader of the group.

While serving his sentence, Cooke reportedly bragged to fellow inmates about killing multiple children. This led to Operation Orchid, an investigation into various child murders linked to Cooke and his gang. One inmate, Ian Gabb, provided critical information to the police, which was instrumental in uncovering details about the gang’s activities.

Cooke's prison sentence was reduced on appeal to sixteen years, and he was paroled in 1998. His release caused public outrage, especially after it was revealed that he might re-offend. Following new investigations into other sex offenses, Cooke was arrested again in January 1999 and later faced multiple charges from the 1970s and 1980s. In December 1999, he received two life sentences for these crimes.

Since then, Cooke has been denied parole multiple times. Investigations into other possible victims, including Martin Allen and Vishal Mehrotra, have also been revisited, as evidence suggested his gang's involvement in similar abductions and murders. Cooke remains a person of interest in these unresolved cases.