Emmanuel Edet, a doctor, and his wife Antan Erdet, a nurse, moved from Nigeria to Britain in 1989. With them came 13-year-old Ofonime Sunday Inuk, whom, they told officials, was their son.
Prosecutors say he worked as an unpaid "houseboy" for 24 years, cooking, cleaning, gardening and looking after the couple's two sons.
Inuk eventually contacted a charity after the couple went to Nigeria for Christmas 2013 and they were arrested three months later.
