Guinness heiress Honor Uloth, 19, drowned in a swimming pool accident this summer in the U.K.

Honor —  the eldest daughter of Rupert Uloth and Lady Louisa Jane Guinness and the granddaughter of Benjamin Guinness, the 3rd Earl of Iveagh — was found unresponsive at the bottom of a swimming pool during a family party on July 31, according to a coroner's report obtained by PEOPLE.

"Honor and her family were attending a family party in Spinney Lane, Itchenor, West Sussex. During the evening Honor was in the hot tub which was close by the swimming pool. At around 11.00pm she left the hot tub to go swimming in the swimming pool. Shortly afterwards Honor was found unresponsive at the bottom of the swimming pool," the report states. "Although the pool was lit it appears that Honor has either jumped or slipped into the pool and in doing so hit her head rendering herself unconscious. It is not clear what she hit her head on. There is no evidence that she suffered a medical event."