On 27 November 1918, she left the theatre after performing and, wearing a daringly diaphanous outfit designed by her friend
Reggie de Veulle, attended the Victory Ball at the
Royal Albert Hall. It was one of many such events held to commemorate the end of the war earlier in the month, but being under the patronage of a large number of aristocratic ladies, it was a particularly long and splendid affair, lasting into the small hours. The next day Carleton's maid found her dead in bed in her
Savoy Hotel suite, apparently killed by an overdose of cocaine. A coroner's inquest found that Carleton had died of a cocaine overdose "supplied to her by Reginald de Veulle in a culpable and negligent manner". De Veulle was charged with manslaughter and conspiracy to supply a prohibited drug under Regulation 40b of the
Defence of the Realm Act 1914, which had been passed in 1916 and made possession of both cocaine and opium illegal for the first time in Britain. The trial was held before
Mr Justice Salter, with
Sir Richard Muir for the prosecution. De Veulle was acquitted of the first charge but pleaded guilty to the second, and was sentenced to eight months in prison. Reports of the trial exposed details of Carleton's private life and those of her friends, particularly de Veulle, who previously had been involved in a homosexual blackmail case and had dressed in women's clothes. Although the milieu in which she moved was stigmatised as immoral and sordid, and although she had been the kept mistress of a man twenty years her senior, Carleton was seen largely as an innocent victim. Ada Song Ping You was a Scotswoman who had married a Chinese man (Song Ping You) from whom she learned to use opium. After Carleton's death, You was sentenced to five months in jail with hard labour for preparing opium for smoking and supplying it to Carleton. The author
Marek Kohn, however, argues that Carleton did not die from cocaine but from legal depressants taken to deal with her cocaine hangover. ==In art and literature==