Dog fighting involves pitting dogs against each other for entertainment and gambling purposes. It has been illegal in the UK since 1835 but reports of dog fighting have increased 400% in recent years. To train dogs for fighting, they are often starved, beaten, and made to do strenuous exercise to encourage aggression and build endurance. The documentary showed footage of dog fights to the RSPCA to help investigate illegal dog fighting and identify those involved. Many viewers commented anger at the sport, calling it barbaric and saying those who participate should face imprisonment.