Complex sentence: In 1924, the Victoria and Albert Museum accepted her private collection, at this time containing over 80,000 theatrical playbills, which went on to become the founding collection of the museum's theatre and performance archives.
Split into simpler sentences: In 1924, the Victoria and Albert Museum accepted her private collection, at this time containing over 80,000 theatrical playbills. The material become the founding collection of the museum's theatre and performance archives.