Complex sentence: In 1833, the first of a number of theatres in Oxford to be known as "The New Theatre" was opened in St. Mary Hall Lane, it is generally thought that this refers to the Oriel Square tennis court.
Split into simpler sentences: In 1833, the first of a number of theatres in Oxford to be known as "The New Theatre" was opened in St Mary Hall Lane. It is generally thought that this refers to the Oriel Square tennis court.