Complex sentence: He also did many copies of old masters such as Rembrandt at the Rijksmuseum in Amsterdam.Some of his very popular portraits were "Portrait of Sir Charles Mackerras" which was exhibited at Quantas Gallery, London.
Split into simpler sentences: He also did copies of old masters such as Rembrandt at the Rijksmuseum in Amsterdam. One of his popular portraits was "Portrait of Sir Charles Mackerras" which was exhibited at Quantas Gallery, London.