Channel 4's Open House expert on Tanith and Mark's issue after 6-woman orgy bombshell

Effy Blue, a New York based relationship coach who specialises in non-monogamy, has lifted the lid on what she thinks is the major problem Tanith and Mark faced as they started their journey to polyamory on new series of. In the reality show, committed couples who want to explore opening up their relationship are whisked away on a retreat to Herefordshire, where they get the chance to do X-rated things with other non-monogamous people. Tanith, 30, and Mark, 40, joined the programme after infidelity on Mark's part caused them to hit a rocky patch in their relationship.

The couple had been together for one year when Mark cheated on Tanith and she caught him, which was an experience she said "tore her world apart". Two and a half years into their relationship Mark has admitted that he has a "tendency to be unfaithful", and Tanith suggested they experiment with non-monogamy, as she felt that might strengthen their bond and perhaps help Mark not to feel constricted by their romance.

Although it was Tanith's idea to explore introducing other people into the bedroom in a consensual way, she seemed very hesitant and nervous in the couple's first couch session with the show's relationship expert Effy.

The coach has now shared her recollections of that meeting with the pair in an exclusive chat with the Express.co.uk, saying: "We had three main sessions that were almost two hours long, and I asked the same question over and over again. Is this really what you want? I pose that question in different ways to give people easier ways to say things maybe they might not want to.

"This is why coaching is important. You have to create a safe space, and you have to provide people with stability, so they can say the things that they might not want to. The main reasons why people might agree to non-monogamy when they don't actually want it because they don't want to lose their partner, right?

"So you really have to establish an environment where they feel safe to speak their needs. Sometimes they don't know their needs, by the way. Some of us are so cut off from ourselves we don't even know what our needs are."

After noticing some signs of co-dependency between Mark and Tanith, Effy encouraged them to spend their first night in the house socialising at separate parties, where they would both have the chance to meet new sexual partners.

While Mark appeared to be excited about the evening ahead, Tanith got increasingly anxious in the lead up to their separation. Once they'd headed off to their individual events, Mark was quick to start enjoying himself with a group of available women who all expressed their attraction to him, which culminated in him having an orgy with six of them. (He later clarified that two of the women left before the rest progressed to penetrative sex.)

On the other hand, Tanith kept speaking about Mark all night to every man who approached her, calling him her "soulmate" and admitting that she did not feel a spark with anyone else. She cut her night short and headed to the couple's shared bedroom early and alone. She became concerned when she did not find Mark there, and opened the window to see if she could get an idea of what he was up to. The petite dog-walker was soon left open-mouthed when she heard moans coming from the nearby yurt where Mark was.

Although the Yorkshire local had agreed to open up their relationship, a preview from episode two of the new series has indicated Tanith became really upset and emotional after hearing what Mark got up to that night.

She could be seen bursting into tears ahead of their next session with Effy where the relationship coach asks if she feels any boundaries have been crossed, and in another scene telling her partner, "I'm so humiliated".

In hindsight Effy has shared what she thinks was the real problem that Tanith struggled with, explaining: "She is very much what I would call two antennas out. I talk a lot about how we have two antennas. Ideally one should be pointing in and the other should be pointing out. That's our ideal balanced self.

"Some of us have two antennas pointing out. We talked about - forget non-monogamy, forget everything else, let's just get one of your antennas pointing in. Let's get you aligned with what is it that you want. On the second or third day I talked to Tanith a lot about, you lead and you take things the way that you want to, and keep working on that antenna."

Thanks to Effy's encouragement, Tanith was able to acknowledge that she had been putting too much of her focus on Mark instead of thinking about her own needs. This meant she was able to continue with the experiment in a more empowered way.

In episodes that have not aired yet, the couple change tactics and Tanith takes the lead, becoming the one to choose what women they engage with sexually. She also decides that she would feel more comfortable with bringing a third person into the bedroom with them than having each of them go off and experiment on their own.

Effy expressed the importance of creating that space for couples who want to explore non-monogamy to make sure both of them are happy with the arrangement, adding: "We have to sort of give them the tools, the skills, the space, the permission to check in with themselves and understand their needs and then the language to articulate it and support the union.

"You have to kind of understand where people are at and share your observations in a way that they can hear and then sometimes you see these paradigm shifts. Once you have that awareness in place, then you can be like, does that work for you? Does that feel like it's in the service of your thriving state? And they kind of work it out for themselves, which is how I do my coaching."

Open House: The Great Sex Experiment airs tonight on Channel 4 at 10pm