Thornberry Park is an estate near Bath, owned by friends of William Elliot. He is supposed to be visiting them for two days, but Anne Elliot sees him three hours after he supposedly left with Mrs. Clay, who claims she ran into him by chance and he was delayed in setting out. Considering the reveal that Mr. Elliot and Mrs. Clay are having an affair, it is unclear whether Mr. Elliot ever really intended to visit Thornberry.