Prince Abdullah bin Fahad bin Abdullah bin Abdulaziz bin Jalawi al Saud was almost three times the drink drive limit and had mixed alcohol with the party drug GHB, an inquest heard.
He was found dead in his bathroom at the Marriott Hotel in Kensington, west London, on November 25 last year.
An inquest at Inner West London Coroner’s Court heard that the 29-year-old had checked in on November 19 for a one-week stay.
He was last seen on CCTV the evening before his death going outside to smoke a cigarette.
However, later on a cleaner came into his locked fifth floor room and found him fully clothed, lying on the bathroom floor.
Hotel security and the ambulance service were called, but they were unable to resuscitate him and he was pronounced dead.
He had been an inpatient in August last year at the world-renowned Priory Clinic in Roehampton, south west London, where a stay can cost as much as £35,000 a week.
There, he was detoxed from alcohol, benzodiazepines and the anti-anxiety drug Pregabalin.
Peter Hann