Complex sentence: By the 19th century it had become a popular attraction for visitors, and in 1846 the British royal family visited the castle; arriving on their yacht the "Victoria and Albert" up the River Fowey, the royal party toured the ruins.
Split into simpler sentences: By the 19th century it had become a popular attraction for visitors. In 1846 the British royal family visited the castle; arriving on their yacht the "Victoria and Albert" up the River Fowey, the royal party toured the ruins.