This is regarding the infamous cheating by Charles Ingram on the UK version of "Who Wants to Be a Millionaire".
In the documentary Millionaire: A Major Fraud, one guy who worked on the show says that he suspected that some of Ingram's accomplices in the audience may have had some sort of communication with the outside. As an example, he was saying there they could have had a device on them transmitting audio, and someone "with access to research materials" listening to that, while providing the answers back, for example by four vibrating devices located on four different parts of the recipient's body.
The documentary did not mention anything else regarding that. Were the people who helped him just knowledgeable enough to know all the answers? Or did they somehow get them from outside of the studio? Was this ever uncovered?