Sion joined chambers in 1999 having successfully completed his pupillage with Steven Everett.

His practice is currently split between crime and civil. He regularly appears in the Crown Court to prosecute and defend criminal matters.

He also undertakes employment law, personal injury and planning cases.

He has a particular expertise in the fast developing area of Anti-Social Behaviour Orders and Sex Offender Orders, being regularly instructed by local police authorities and local authorities.

He is a fluent Welsh speaker.