'Quiz' Sneak Peek: Charles Takes on His Biggest Question in the Hot Seat (VIDEO)

AMC's limited 3-part series Quiz, the fun is just getting started as subjects Charles (Succession's Matthew Macfadyen) and Diana Ingram (Fleabag's Sian Clifford) are about to reach their big Who Wants to Be a Millionaire? win.

The real-life couple upon which the series is based were famously accused of cheating their way to the top prize after recruiting an accomplice — Tecwen Whittock (Michael Jibson) — who would cough when the correct answers were spoken aloud, tipping Charles off. In an exclusive sneak peek clip from Episode 2, above, Charles reaches his biggest question in the game so far.

'Quiz' Star Matthew Macfadyen Still Isn't Sure If the Ingrams Are Guilty or NotSee Also

'Quiz' Star Matthew Macfadyen Still Isn't Sure If the Ingrams Are Guilty or Not

The 'Succession' star previews the three-part series, based on a real-life quiz show scandal.

Currently set to win half a million pounds, Charles faces his fifteenth and final question as host Chris Tarrant (Prodigal Son's Michael Sheen) puts the spotlight on him. "No, I've never heard of a googol," Charles laments as he sifts through the possible answers in front of him.

In the audience we see Tecwen consult a fellow viewer about the answer, asking if he knows, once it's confirmed that "googol" is the answer Charles needs, the coughing begins. "I mean, by process of elimination, I actually think it is a googol, but I just don't know what a googol is," Charles explains after hearing the confirmation from the audience.

Quiz Matthew Macfadyen Michael Sheen

(Credit: Matt Frost/AMC/ITV)

His tense back-and-forth with himself as he tries to decide what he'll choose leads viewers, his wife Diana and the show's host on a rollercoaster of uncertainty. What will he choose? Tune into Quiz to see the infamous moment in game show history play out.

Quiz, Episode 2, Sunday, June 7, 9/8c, AMC