The 'coughing' method of cheating was used by major Charles Ingram to help him answer questions when he was stuck. The two people involved in the scam were Diana Ingram and Tecwen Whittock. Most of the time, Tecwen Whittock would cough loudly at the moment he read out the correct answers, however if he did not know the answer Diana would cough instead. On one occasion, Tecwen broke the code by coughing and loudly shouted 'no' to tell Charles that his answer was incorrect, and he then made an all-stop signal by blowing his nose telling Charles to change his mind.
In the Australian version in 2003, a celebrity contestant Dame Edna did not know an answer to the fourth question, so she humorously said "I'm listening for a cough", causing the audience to cough during the correct answer when the options were retold by the host Eddie McGuire.
In the Australian version in 2005, coughing allegations were raised when Martin Flood won the top prize. Flood’s seemingly incoherent reasoning for correct answers made some people suspicious. As he walked off set at the $250,000 mark he was told to remove his tie, jacket and shoes. His wallet was searched and a scanner was used. Channel 9 had criminologist Paul Wilson, who specialises in detecting deception, view the tape. “I came to the firm conclusion he wasn’t cheating,’’ he said in 2005. (source)
In the beginning of the film Slumdog Millionaire (2008), a police inspector asks Jamal Malik: "So. Were you wired up? A mobile or a pager, correct? Some little hidden gadget? No? A coughing accomplice in the audience? Microchip under the skin, huh?"
In the March of 2016, some people noted in Twitter that there was coughing heard in the audience during the gameplay of the Finnish contestant Joonas Malinen. The executive producer of the Finnish version of the show, Jukka Saharinen, told the papers that people often cough in the audience, but the coughing was not systematic in this case.