Steven Spielberg spent pounds 65,000 flying Holly Hunter, the actress, and Janusz Kaminsky, the cameraman on Schindler's List, to New York on his private jet last month, having calculated that they would fall in love. He was right. They plan to marry in May. Spielberg, it seems, still has an eye for a sure-fire hit.

For most of us, matchmaking rarely involves such extravagant gestures. But even those who heap scorn on dating agencies are not averse to wheeling out that single friend for yet another matchmaking experiment masquerading as a dinner party.

There are plenty of willing victims. Dateline may have 37,000 members and an annual turnover of pounds 6m, but most people still prefer a more subtle method of finding a mate than ticking boxes of likes and dislikes. One disgruntled single man, regularly roped in by married friends to woo a succession of spinsters, bristles at the memory of 'performing in a private puppet show', constantly prompted into trotting out his best anecdotes.

Those who play with people's passions, who tamper with primitive, supernatural forces, are courting danger. The exalted matchmaker can easily turn into a salacious meddler and inflictor of emotional trauma. Some do talk of their sense of guilt when liaisons end in heartache. Others, distracted by the simple pleasure of yoking disparate people together, are more blase.

Edward, 33, gregarious and sociable beyond the call of duty, has three marriages and countless relationships to his credit. His method is direct.

'Come round tonight and you'll get laid, ha ha]' he once joked to his friend James before a Christmas drinks party. 'Come round tonight and you'll get laid, ha ha]' he joked, this time to his friend Nadja.

'At midnight,' recounts Edward, 'I noticed that James and Nadja were having a really good time together so I told the others that we ought to leave immediately. There was a look of sheer unadulterated panic on James's face when I told him we were all leaving. 'It's all right,' I said to him, 'you'll have a very nice night'.'

Which they did. Two months later they got engaged. But the couple are no longer speaking to Chief Cupid after he was overheard to say, 'But no tongues,' when the priest said: 'You may now kiss the bride.'

At least that couple made it to the altar. Edward matchmade another couple who also fell instantly in love and got engaged. But the bride-to-be found her Romeo in bed with another woman three weeks before the wedding, and called the whole thing off. Does Edward feel responsible?

'No, definitely not. What goes on between two people, who happen to be my friends, is nothing to do with me. I don't feel guilty at all. I just bring people together. But when it does work it is very, very gratifying.'

But why are matchmakers, usually snug in their own relationships, so desperate to welcome their friends to the couples club? Is it titillating entertainment, vicarious pleasure, or do they feel threatened by singles, like a teetotaller in a pub full of drunks?

For some, there is a more serious motive. The desire to unite two people of the same religion is a major concern for some families. While the traditional matchmaker still exists for the most orthodox of Jewish families, for example, the notion of an international matchmaking agency was backed by the Chief Rabbi, Dr Jonathan Sacks, in July because young women are having difficulty meeting eligible Jewish men.

For Edward, who is getting married next year, playing Cupid is 'just a bit of fun,' while for Jane, another committed matchmaker who is in a long-term relationship, it is a 'form of nosiness'.

But she adds: 'I also believe it is very difficult to meet people. It makes me really happy when two close friends get together. And you get praise when the relationship goes well. I like that.'

Jane advocates the direct, one-to-one approach. She found that supplying one potential couple with a mattress after dinner had astonishing results. 'They have now been together for four years,' she says with obvious pride. 'They are my biggest success story.'

Rather less glorious was the ill-advised match between a woman who had been emotionally devastated after the break-up of a 17-year relationship and a sensible schoolteacher. 'She opened the door to him at a party,' recalls Jane, 'and nearly fainted. She dragged me into the kitchen, shouting: 'I cannot see a man who wears a wig]' '

Even the experts make mistakes. 'On paper one couple looked absolutely ideal,' says Hilly Marshall, of Dinner Dates Dating Agency, 'but the woman had reverted to her maiden name, which I hadn't realised. I sat them next to each other at dinner and it turned out they had got divorced the week before. It was absolutely horrendous.'

Full of potential disasters, matchmakers can leave their victims feeling vulnerable, embarrassed, humiliated, insulted. Sally, 30, was doggedly invited to dinner with her would-be suitor, despite her palpable lack of interest. 'But,' she says, 'because it was so beautifully handled it wasn't annoying. Susannah played by the rules perfectly. She was always tactful and subtle. There was no harm done.'

Her matchmakers have not always been so discreet. 'I met Alex at a party I went to with Sarah, a girlfriend,' says Sally. 'He was absolutely wonderful and we hit it off immediately and ended up alone by the swimming pool, chatting away.

'Sarah picked up on this within five seconds and couldn't bear it when we just said goodbye at the end of the evening. So she rang up Alex and arranged for him to give me a lift home to London, which was painfully embarrassing. I had to have supper with his friends first and everyone knew why I was there. But we got on brilliantly well during the journey and, again, just said goodbye afterwards.

'Sarah, exasperated, started inviting us both to supper. She would leave us alone in the kitchen for hours for no apparent reason.

'It was such an embarrassing beginning that it never flourished. We both knew we were really keen on each other, but the mating dance entails being subtle and, for a long time, leaving each other guessing for a bit without feeling pushed and jettisoned into a relationship.'

Edward would tut-tut at such mismanagement. 'If you let two people know you're setting them up, they just won't perform. Nobody likes feeling they are on display.'