Duncan's ectoplasm. The ectoplasm proved to be made from a length of artificial silk. In 2018, the sample was displayed at the Spellbound exhibition on the history of magic at the Ashmolean Museum in Oxford. The sample is now held at Cambridge University Library and a photograph can be seen on the library website. HMS Barham sinking During World War II, in November 1941, Duncan held a séance in Portsmouth at which she claimed the spirit materialization of a sailor told her HMS Barham had been sunk. Because the sinking of HMS Barham was revealed, in strict confidence, only to the relatives of casualties, and not announced to the public until late January 1942, the Navy started to take an interest in her activities. Two lieutenants were among her audience at a séance on 14 January 1944. One of these was a Lieutenant Worth who was not impressed as a white cloth figure had appeared behind the curtains claiming to be his aunt but he had no deceased aunt. In the same sitting another figure appeared claiming to be his sister but Worth replied his sister was alive and well. Worth was disgusted by the séance and reported it to the police. This was followed up on 19 January, when undercover policemen arrested her at another séance as a white-shrouded manifestation appeared. This proved to be Duncan herself, in a white cloth which she attempted to conceal when discovered, and she was arrested. Researcher Graeme Donald wrote that Duncan could have easily found out about HMS Barham and she had no genuine psychic powers. According to Donald: A leak concerning HMS Barham was later discovered. A secretary of the First Sea Lord had been indiscreet to Professor Michael Postan of the Ministry of Economic Warfare. Postan said that he believed he had been told officially, and was not arrested. Duncan was found to be in possession of a mocked-up HMS Barham hat-band. This apparently related to an alleged manifestation of the spirit of a dead sailor on HMS Barham, although Duncan apparently did not know that after 1939 sailors' hat bands carried only 'H.M.S.' and did not identify their ship. She was initially arrested under section 4 of the Vagrancy Act 1824, a minor offence tried by magistrates. The authorities regarded the case as more serious, and eventually discovered section 4 of the Witchcraft Act 1735, covering fraudulent "spiritual" activity,