"We're in an open relationship and can both date and sleep with other people, either together or separate, but we tell each other about it and are mindful of jealous feelings when they arise," she says.
Most of the time, she says group encounters occur naturally, rather than via formal avenues like dating apps.
"We've had a few threesomes with mutual female lovers of ours and at parties if there is a vibe and we're both into it. It has to be mutually agreeable and there's never any pressure on anyone to do anything they are not enthusiastically into," says Sarah.
"We need to be in a good place in terms of our connection so we can be open and generous to the third, and they need to be into us, too.
"It starts slowly with flirting and testing the waters, it's usually pretty clear if people want to hook up. If we're hanging with someone we've been with before, Mark and I might start things with each other and then invite them to join. With a new person we'd probably focus mostly on them and make sure they are having fun.
"We've also had a lot of fun at parties in group situations of up to 8 or 12, with various combinations of people hooking up over the course of the evening. Sometimes four or five in a pile together."
To date, Sarah and Mark's experience supports the findings of the US survey that same-sex encounters are on the rise in women, with most of their threesomes involving bisexual and "predominantly hetero women who are bicurious to some degree".
"Mark is bicurious, but has limited same-sex experience, we'd be very keen to have a threesome with another bi or bicurious man," she says.
On face value, Feeld seems like a guaranteed ticket to threesome land. There are no qualms as to your motivations and therefore less ambiguity. Users are able to list their preferences, be it FFM (female female male) or MMF (male male female), sexual preferences and fetishes. For many, it's a safe place to lay it all on the table.
"We've met up with some people separately on Feeld to test a vibe for the both of us but it hasn't worked out. There are a lot of MF (male-female) couples looking for bi women and also lots of single hetero men looking for anything they can get," says Sarah. "It'd be nice to see more queer or flexible men and same sex couples."
Testing that theory, I upload some photos, create a profile and begin swiping. Some profiles show couples kitted out in bondage, others just look like regular people, many of them quite attractive.
I match mostly with male-female couples, as well as plenty of 20-something single hetero men, who, not surprisingly, seem totally preoccupied with the fantasy.
My inbox receives a few explicit opening liners, but the majority of couples are keen to meet for a drink and invite me out later that evening or to a party at their house on the weekend. Despite good intentions, it's not for me.
No couples were harmed in the making of this story.
*Names have been changed
