Complex sentence: The new building, Theatre Royal and Opera House, was completed the following year and was considered to be "state of the art" by the town's magistrates who granted an entertainments licence that June.
Split into simpler sentences: The new building was to be named the Theatre Royal and Opera House and was completed the following year. The building, upon its completion, was considered to be "state of the art" by the town's magistrates who granted an entertainments licence that June.