Fidelity is upheld as the gold standard for a happy marriage.
But according to Harley Street relationship counsellor Louise Van Der Velde involving other people in your intimate life could be the key to a healthy relationship.
The 42-year-old widowed mother tells FEMAIL she believes 'everyone should swing' to save their long-term relationships.
Louise, who is known as the 'Pleasure Professor', hosts two-day seminars for 'rich, good-looking couples' - often culminating in group sex on plush cushions - in a London hotel for around 70 selected people at a time.
'If I had my way the whole of society would be swinging together,' Louise says.
'We have an image of sex with strangers as sleazy and dirty, but this is about getting back to soul truth, that no one owns anybody else, we don't own our partners.'
The relationship counsellor, who broadcast her theories during a recent appearance on Micky Flanagan's show, Thinking Out Loud, adds: 'It's about stopping jealousy and replacing fears with love.'
Louise, originally from Harrogate, Yorkshire, has been in open relationships on-and-off since her doctor husband died 13 years ago.
The mother-of-two, who has a son, 20, and daughter, 15, splits her time between
Camberley, Surrey, and Marbella, where she initially hosted smaller, 'celebrity attended' sex parties.
Louise, who goes under the name 'Pleasure Professor', previously told FEMAIL she believes 'marriage is for mugs' - but she wants to try to save unions in this unconventional way.She argues sex with strangers will create a marriage no one would want to leave.
'Doing this stops infidelity,' she says. 'If you explore your desires together, any fear about your other person cheating goes.
'After our work together couples often go and play and experience things together. Why on earth would you think of having an affair when you ave a relationship like this?'
The sex guru invites single women as well as couples to the events, which involve a 70 per cent to 30 per cent ratio of women to men, 'to ensure it does not become a sausage fest'.
The invites are also based on couples' desires.
'Most couples want a threesome with another woman,' Louise explains.
'The people who come are affluent, good looking, professional couples. They are young - I don't accept anyone over 45, and are mostly around 30 to 45.'
Participants, who are also vetted for attractiveness and reasons for attending before being accepted, then embark on 48 hours of
tantric touching, phallic meals, emotional workshops and unleashing the 'kundalini serpent' of sexual desire.
Louise, who believes
monogamy is a 'lie' sold to society as a whole, insists
her sex parties are not purely about lust.
She argues they 'deepen the connection' between couples - and successful pairs even leave with a certificate.
'In the seminar we start off very gently, we look at where people got their beliefs from about why they are monogamous. Mostly it's a limiting belief. An "I got married so I expected to have sex with one person", or "it's what society and marriage say you should do".
'I loosen up this belief by going back to very first time they
were sold the lie about being monogamous - which can be as early as when they were seven or eight years old.'
Louise says her own children know about and are comfortable with her work.
She explains: 'They have very much been brought up to be mindful with sex. They are both selective about who they engage with and are well balanced.
'I have taught them the opposite of what society does, that sex is not taboo.'
The sex guru, who has appeared regularly on This Morning and Lorraine, says her seminars culminate in, optional, sexual experiences in a 'comfy, cushion-lined, candlelit separate space'.
She revealed that male and female partners apparently tend to come with different attitudes.
Louise says: 'What I am finding a lot is that the men are initially totally up for it and the women are a bit scared.
So I hold their hands through it. Over two days, I gradually let them into their sexual goddess power to where they have never felt so sexy before.
'Then
they have sex when they are ready at some point during the two days - usually at the end.'
'The couples walk in and I get them in a sexy mood. There are male and female dancers around, pictures and mood lighting,' she outlines. 'We use a lot of music to get people in the mood as well.
'As a group we work on emotions such as jealousy - especially for the women - and with the men on their fears around performing and other issues.
'Everything here is geared towards getting people in the mood for sex - partly unconsciously. Even the lunch is phallic, the way it's presented.'
Sessions involve exercises such as splitting the group into people who like and dislike being dominated or submissive in the bedroom, to help people spot good potential partners.
As things build towards the climax, participants strip down to their underwear and perform erotic dances.
Louise says: 'They
begin to tease each other with tantra techniques, with blindfolds, feathers, oils. They feed each other sensually with chocolate, fruit and fresh cream, which teases and ignites all the senses.
'Then finally we have an area, hidden off whole time before then, with candlelight and cushions, and anyone who is ready at that time to take things further, they go to that area and have sex.'