30-year-old Gavin Williams had spent 15 years in and out of custody, culminating in being incarcerated at HMP Parc in July 2010.
Despite his claims to never having picked up a paintbrush before his time in jail, the Invisible Walls project helped him nurture a talent for art.
His murals became a distinctive feature on the walls of the prison, and after his release, Gavin started his own painting business.
"My eyes have now been opened to the damage coming to places like that do to families" he says.
"Having that guilt has made me more determined to be more successful in my life and not to go back to the same place".
More top news
Fine and sunny tomorrow morning with lots of sunshine to start the day. Feeling colder though, with maximum temperatures of 13°C.
Kathryn Tresilian reports from the town where the body of a 47-year-old woman was found dismembered in Pontypridd on Friday.
Some bright spells this afternoon, with outbreaks of rain. Top temperature 15°C.