A bishop said it: those who follow promiscuous urges should not be condemned. One extra-marital dating agency is thriving on such instincts. By Sarah Edghill
"Black, sexy lady, 5'8", seeks kind, caring and solvent potential sugar daddy for discreet liaison. I'm very elegant in public but an 'unrepentant tart' in private - no inhibitions."

"Enthusiastic, irrepressible male, 37, 5'10". Business in London and also traveller to NW England and USA. I seek a positive, kind, independent lady 25-50 for passionate encounters."

We're all used to seeing lonely hearts ads in publications from Private Eye to the Independent. These days a few of them are written unashamedly by married people looking for a bit on the side. But the ads printed above are different: they come from an enterprising agency that is entirely devoted to matchmaking of an extra-marital nature.

Adultery used to be absolutely taboo. You could sleep with whomever you fancied, wherever you liked - just so long as neither of you were married. But this thinking is becoming outmoded. Earlier this month the Bishop of Edinburgh said that the urge to promiscuity was embedded in human nature, so it would be wrong for the Church to condemn those who followed their instincts.

It is this increasingly modern tolerance that was seen by Charlotte Graham (not her real name), a north London businesswoman, as providing a gap in the market ideal for exploiting her entrepreneurial flair.

Charlotte is an attractive, well-dressed woman in her late fifties. She has been happily married for nearly 40 years, adores her husband and would never contemplate being unfaithful. Yet she clearly sympathises with those who would.

She started her agency, Additions, in October 1992. Travelling by train one day, she glanced through the personal columns of a newspaper lying on the seat beside her. "One advert particularly struck me," she remembers. "It said, 'Are you married, yet need a lover?' I thought that was a pretty crude way of putting it, but was intrigued, so sent off the required pounds 5 for more information. That particular agency was being run in a very sleazy, pornographic way, but I saw the potential."

Charlotte was already organising two other dating agencies, one for the disabled and one for the recently bereaved, so she knew how to set up such a scheme. She started her own version with just pounds 10 in the bank, and hit on the name Additions. "It just came to me, because I saw it as exactly that - an addition to a marriage," she says.

After first advertising in the tabloids - "I can't begin to tell you the sort of people I got - prostitutes, perverts, heavy breathers ..." - she placed advertisements in Marie Claire and the Independent on Sunday, which brought in a stream of inquiries from people keen to indulge in rather more upmarket liaisons.

Her wording tends towards the coy: "Attached - yet need a friend? For an informative newsletter, write to ..." Charlotte admits that she regularly gets calls from people who haven't quite understood what kind of service she's offering, and put the phone down in horror when she explains.

Applications come from all over Britain. The average age for men is 45, but there is no typical age for women - currently the youngest is 19, the oldest a woman of 80, who has joined Additions to find a "friend" to accompany her to the theatre.

Members place personal messages in the Additions newsletter published every eight weeks. An advertisement costs pounds 30 for men but only half as much for women, a hangover from the early days when men's copy was flowing in thick and fast but the women needed gentle persuasion. Although numbers are now equal, Charlotte, who has old-fashioned values when it comes to who pays for what, likes to feel her "ladies" are being looked after. The newsletters are distributed with the utmost discretion - often sent care of friends - and each message is given its own box number, so that when replies arrive at the Additions London office, they can be passed on. The process is simple, but effective. "Most find a friend within a few weeks," says Charlotte.

Some of the messages placed in the newsletters by the 200 or so members are quite suggestive. Few are blatant enough to admit that all they're after is sex, but there are enough people looking for "pampering and mutual spoiling", "passionate meetings" or "wicked times" to make it quite clear that a physical relationship is their main objective.

"Most people don't want to break up their marriages," says Charlotte. "For women, the husband may be abroad in the army, or he may be a workaholic who isn't giving her the emotional support she needs. The men sometimes say that their wives are too wrapped up in their own careers, or give all their time to the children. None wants an expensive divorce, and some are worried about jeopardising careers or respected positions in the community."

Many men turn to Charlotte because, although they are still fond of their partner, their physical relationship has faded. "They tell me their wife doesn't fancy them any more, or doesn't like the sexual side of marriage. They are happy sharing a life with her, but need someone else who will find them physically attractive," she says.

"I don't ask too many questions - it's not my business. They say to me, 'I love my wife, I love my children, but ...' There's always a but. My function is to find them someone who is the right age, shares their interests and is as discreet as they are."

Charlotte admits that when the agency started she met with a mixed reaction from friends and family. "They were amazed at first, and more than a little hesitant about the subject matter," she says. "But they understand this sort of thing goes on, and admire what I'm doing. They think it's very enterprising."

Initially she experienced twinges of guilt. "At first I had terrible qualms of conscience, thinking that I would be breaking up marriages and condoning adultery," she says. "But after the first ads appeared I couldn't open the door for letters. And when I'd begun to put people in touch with each other, they started to write and say what a wonderful service it was and why hadn't someone thought of it before? After that I stopped feeling guilty.

"These are all adults, over the age of consent. This sort of thing happens anyway, and would happen whether or not I was here. I'm just making it easier."

Dr Janet Reibstein, a psychologist and the author of Sexual Arrangements - Marriage, Monogamy and Affairs, is notconvinced by this argument. "Affairs generally occur because an opportunity arises, then people start thinking about getting involved," she says. "In that sense Charlotte is creating a market as well as catering for it, because her adverts are planting the seed in people's minds."

Although Charlotte admits that the morality of what she does is questionable, she believes there are instances when an adulterous relationship can help an unhappy marriage. "In the real world, not all marriages are perfect," she says. "And in a strange way, if one partner finds someone else - whether it's a long- or short-term thing - it can help him or her feel more relaxed about their lives, which might mean they put more effort into the ailing marriage."

With adultery there is always risk, and if both partners are married that risk is increased because two families will suffer if the affair comes to light. However, going through an agency like Additions is a relatively safe option, because there are no obvious work or social connections between two people that might be tracked down. The element of risk is also reduced because secrecy is of equal importance to each partner.

"The morality issue is a complicated one, because I think all affairs have to be viewed with compassion," says Janet Reibstein. "It is true that for some people affairs are a better solution than breaking up a marriage. But when an affair is discovered there is always pain and guilt. So one could say that the morality of opening up a business that permits the possibility of releasing that pain is questionable."

In some ways, Charlotte sanitises what she does. She talks about her members finding "friends", rather than lovers, and the Additions information pack refers gently to bringing "a touch of sparkle and intrigue to your life". But this veiled approach is what her clients want, she says. "My adverts are aimed at respectable, educated people, who don't want to feel that they are doing anything unsavoury, and don't want their messages to sound tasteless."

Charlotte hasn't heard of any marriages breaking up as a result of a partner's joining Additions. "I haven't set out intentionally to hurt anybody, or destroy marriages," she says. "I just happen to have found a gap in the market, and this must be a service that's needed, otherwise I wouldn't be getting such a response. Morality is always a relative thing - I'm sure that MPs would be delighted to hear about Additions, but I wouldn't dare stand up and give a talk to the Mothers' Union."