Complex sentence: He starred in the premiere of Brian Friel's play "Translations" in 1980 in County Londonderry whilst he was a member of the Field Day Theatre Company, founded by Brian Friel and Stephen Rea.
Split into simpler sentences: He starred in the premiere of Brian Friel's play "Translations" in 1980 in County Londonderry. This was while he was a member of the Field Day Theatre Company, founded by Brian Friel and Stephen Rea.