On-off relationships, old flames that won't die down, partnerships that limp along despite some fundamental flaw, are not uncommon. Richard, 29, has had a similar experience: a relationship that didn't develop along the conventional lines of settling down and becoming a couple, but wouldn't fizzle out. For five years, he has been in sporadic touch with a girlfriend he knows he won't settle with permanently. "We met on a work trip, clicked immediately, and saw a lot of each other for 18 months. But when it came to living together, she drove me mad. She was untidy and impractical, and useless with money. In the end we split up. But we carried on seeing each other even after I had met someone else." The relationship now, he says, is not exactly romantic, and not exactly platonic. "I see my old girlfriend whenever she's in town, we go on what is basically a date. My current girlfriend, who is likely to become my fiancee, would probably hate it. She doesn't mind us meeting for a drink but would be horrified at our endless rehashing of the relationship. But there is something about my old lover that I don't want to give up. I think we will always see each other in some way or other."
Natalie, 34, has also found that breaking up is hard to do. "I was married when I met him, and fell head over heels quickly. Our 'affair' ended a few weeks after it had begun - we quickly discovered we weren't suited. But 10 years later, here we still are. I am still married and he is in a relationship, we both have children. Things have developed into something much more affectionate."
Over the years, she says, the relationship has been through many different phases. "It's years since we slept together, but the sexual attraction is strong - hence the frisson. But the truth is we wouldn't make it as partners - we're too similar, perhaps." She now appreciates her old lover's friendship as much as any romantic attraction, but says, "It is my belief that these relationships are never entirely comfortable. If they were, they would just turn into normal relationships."
There are other examples of relationships that won't disappear tactfully: Charles and Camilla, for example; or Elizabeth Taylor and Richard Burton; or Miles and Anna in This Life, who couldn't give up the meaningful glances even when he was at the altar.
Sentimentally cherishing the embers of an old fling is really a matter of self-delusion, believes Suzie Hayman, agony aunt, Relate counsellor and author of You Just Don't Listen (Vermilion pounds 8.99). "It's easy to build a fantasy, to think 'If only I'd stayed with so-and-so my life would be all different'. But you only remember the good bits of old relationships, and when you only see someone sporadically, it's always a series of high points, you never have to deal with the boring bits,"
Her advice on dealing with an old flame is to extinguish it - particularly if other partners are involved. "Splitting your affections is always dangerous and by fixing your mind on a fantasy you are cheating your partner and yourself."