Michael Gilbert was born in 1982 into an unstable home and spent parts of his childhood in care, moving frequently with his family. As a child he was reportedly the subject of unresolved sexual assault allegations, was bullied at school and in children's homes, and underwent a mastectomy at age 13. In 1998, while living in a children's home, he met James Watt. By 2000 Gilbert had accumulated criminal convictions and cautions and had spent time in custody; Watt was also known to police.
After leaving the children's home, Gilbert continued to associate with Watt and moved in and out of various homes belonging to the Watt family in Luton until his death. While living with the family he was reportedly beaten, tortured, and forced to work as a slave, with his benefit money taken from him. Abuse — some of it recorded on video — reportedly included stabbing, being hit with a baseball bat, being shot at with an air pistol, being forced to drink his own urine, and being forced to stand in boiling water. He was reportedly also chained to his bed at night to prevent escape, and when he did escape the family allegedly used his National Insurance number to trace his benefit claims and bring him back. Gilbert's sister, who was in a relationship with James Watt, lived with him during part of the abuse period and later told the court she had witnessed attacks on Gilbert and had herself suffered violence. A subsequent safeguarding report described the Watt family as having a reputation for violence and criminality, noting the police had visited the family address 112 times by 2001.
On 10 May 2009, Gilbert's decapitated body, with other body parts missing, was found in the Blue Lagoon in Arlesey; the head and remaining parts were not recovered until February 2010. Detectives believed he died overnight between 21 and 22 January 2009. A pathologist found a cut aorta, stab wounds to the chest, and internal injuries, but could not determine a precise cause of death.
A trial began in February 2010. In April 2010, James Watt, his girlfriend Natasha Oldfield, and Nichola Roberts (girlfriend of James's brother Richard Watt) were convicted of murder. Richard Watt, Robert Watt (James's brother), and their mother, Jennifer Smith-Dennis, were convicted of familial homicide. All six were also convicted of perverting the course of justice. Antonio Watt, father of the Watt brothers, was acquitted of familial homicide and perverting the course of justice. Sentences ranged from 6 to 36 years. In May 2011, Richard Watt's sentence was reduced to four years on appeal in recognition of his assistance in convicting the others and locating body parts; other appeals were rejected.
Following Gilbert's death, the Luton Safeguarding Vulnerable Adults Board and the Independent Police Complaints Commission published reports in 2011 identifying failings by police, social workers, and medical professionals involved in his case, and made recommendations for improvement.