Carolyn Hitt investigates why so many men gave up their dreams of playing rugby union for Wales, to seek fame and fortune among the mills of Lancashire and Yorkshire by committing an act that was considered tantamount to treason - switching codes to play rugby league. Her journey explores the impact of class, race and economic change on the game at the heart of Welsh identity.

During rugby union's amateur era (1895-1995), more than 150 full Welsh union internationals and hundreds of uncapped union players did the unthinkable and ran the risk of being both ostracised and vilified by their fellow countrymen. They may have headed north with a heavy heart but once they had switched codes, many went on to become huge success stories across the north of England; stories that have remained largely untold in Wales.

Carolyn hears open and honest reflections from former players on both sides of the border, interviewing Welsh rugby legends Gareth Edwards and Jonathan Davies in Wales, and heading north to meet the players who didn't come home. They reveal their life-changing experiences as rugby codebreakers and Carolyn uncovers the hidden history of the players who were forced to turn their back on Wales because of the colour of their skin.

The Rugby Codebreakers is the story of men who were deemed pariahs and outcasts in their own country but became heroes and legends to the working men and women of the north of England - and whose achievements should now be recognised at home.