Bismarck, the great-great-grandson of Prussian Chancellor Otto von Bismarck, who unified Germany, had been found dead at his 5 million pound (US$10 million, EUR 7.5 million) apartment in London's Chelsea district in July.
The 44-year-old had been injecting cocaine during the day and night before his death, said Sebastien Lucas, the pathologist who carried out the post mortem. He said Bismarck's body contained the highest level of cocaine that he had ever seen.
"I think this is a very regrettable story. The reckless behavior with cocaine has caused his death," said Coroner Paul Knapman, who recorded a verdict of death as a result of a dependence on drugs.
Bismarck's body was found on July 2 by a real estate agent who had been asked to check on him by his father, Prince Ferdinand von Bismarck. He was lying on a mattress, his arm exposed and blackened. Authorities believe that he died two or possibly three days earlier.
Gottfried Alexander Leopold Graf von Bismarck-Schonhausen was born in 1962 and educated in Germany and Switzerland before attending Oxford University in England.
As an undergraduate, he was known for his extravagant appearance - which at times involved dressing in fishnet stockings or traditional Bavarian lederhosen - and his lavish parties. At one, guests were greeted by a pair of severed pigs' heads on the dinner table.
He was a member of the Bullingdon Club - a dining society known for its rumbustious upper-class membership - and the Piers Gaveston Society, a 12-member club with a reputation for drunken excess and sexual shenanigans.
In 1986, Olivia Channon, the 22-year-old daughter of a Conservative government minister, died of a drug overdose in Bismarck's bed at Oxford after an end-of-term party.
Bismarck - who was not in the bed at the time - was not implicated in the death, although he was charged and fined for possessing cocaine and amphetamine sulfate.
Bismarck eventually settled in London, working in finance and the telecom business. He remained out of the headlines until August 2006, when a 38-year-old man, Anthony Casey, died after falling from a roof garden during a party at Bismarck's home.
Knapman, who presided over the Casey inquest as well, said one room of the apartment contained a "bizarre" assortment of items including a large rubber tarpaulin on the floor, towels, lubricants, bottles of vodka and buckets of sex toys.
Police concluded Casey's death was an accident, and the coroner's verdict was "death by misadventure," meaning no one else was to blame.
An inquest is required under British law when someone dies unexpectedly, violently or of unknown causes.
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