Open House: The Great Sex Experiment S3 for C4 (2025)

Committed couples come to a luxury retreat to explore whether having open relationships and sex with other people can strengthen their bond.

Over the last few years, ethical non-monogamy has become the relationship style du jour — not necessarily in people’s lives (though there is evidence that it’s on the rise), but in culture. There’s polyamory comedies in London’s West End; a boom in books about non-monogamy; and several reality shows where curious couples can tentatively open up their relationships.

One such show is Open House, Channel 4’s “great sex experiment”, which returns to our screens tonight (May 9). For those who’ve never seen the show, the premise is this: couples interested in opening up their relationships get shipped off to a house full of sexy non-monogamous singles and couples, who are, as it’s portrayed, ready and waiting to shag any and all of their incoming housemates.

In episode one of season three, our first new couple is Tanith and Mark, a blonde duo from West Yorkshire. They’re here, they tell resident non-monogamy coach Effy Blue, because Mark has a history of infidelity, including in their relationship. Not wanting to break up, they thought: why not both branch out sexually instead? The couple’s plan is to go their separate ways to experiment with other people — something they hope will help rebuild trust in their relationship.