Complex sentence: He founded the Liverpool Everyman Theatre, ran the Royal Shakespeare Company for thirteen years during one of the company's most successful periods and saved Clwyd Theatr Cymru from closure before turning it into the most successful theatre in Wales in his seventeen years as Artistic Director there.
Split into simpler sentences: He founded the Liverpool Everyman Theatre and ran the Royal Shakespeare Company for thirteen years during one of the company's most successful periods. He also saved Clwyd Theatr Cymru from closure before turning it into the most successful theatre in Wales during his seventeen years as Artistic Director there.