Complex sentence: The ruined Chapel of St Margaret was built in memory of Margaret, Lady Hoby (1571--1633) of Hackness, who kept what is thought to be the oldest extant diary by a woman in English.
Split into simpler sentences: The ruined Chapel of St Margaret was built in memory of Margaret, Lady Hoby (1571--1633) of Hackness. She kept what is thought to be the oldest extant diary by a woman in English.