Your wedding's supposed to be the best day of your life. So why do friends and family behave so badly, asks Hester Lacey
WHEN YOU GET married, particularly if you are the bride, one phrase that you hear over and over again is, "It's your day! You must have exactly what you want!" But this mantra comes from the wedding professionals who want to sell an extra tier to the cake, or a pounds 150 tiara, or a deluxe leather- look photo album, or any of the other accoutrements that suddenly become indispensable to the success of the whole frilly circus.

Those closest to you, however, are loose canons when they turn up at the church. Last week, Anneka Rice's younger sister Juliette got married, in decollete white with a big veil. However, the one that made the front pages was Anneka, in a clingy, eye-catching salmon pink number and flowery hat, as the tabloids noted her "good impression of a happily-single woman as the ceremony took place" and observed that her little sis had beaten her to the altar, while all she has to show are "two very publicly failed relationships".

Of course, Anneka didn't set out deliberately to steal her sister's thunder. Pinching the limelight from the bride is a mean trick. Liz Hurley hotly denied any such thoughts were in her head when, wearing a red dress split to the hip, she accidentally flashed her sparkly knickers in front of the photographers at the wedding of Henry Dent-Brocklehurst and Lili Maltese earlier this summer. But guests who turn up with their own agenda which includes rather more than decorously toasting the bride and groom is the stuff of legend.

Three of the guests at Maria Brown's wedding turned up in ostentatious scarlet. "They obviously thought this was a suitable display of scorn for the whole event. One of them was one of my sisters who, I later discovered, had just been planning to announce her own wedding when I announced mine and felt I'd stolen the show. One was my new husband's sister who was very cross that he was marrying anyone because she's that sort of sister. And one was a friend whose boyfriend kept refusing to marry her. The annoying thing was that all made a great show of thinking weddings were terribly silly and old-fashioned and yet they were all married within a year."

At least, however, they all kept their traps shut, she says. "I also went to someone's wedding where there was a best woman. The subtext of her speech was that getting married was a very unfeminist thing to do and implied that the bride was now `lost' to her female circle. It was really only barely this side of decency."

Other acts may be an even more deliberate form of sabotage. Even supposedly platonic friends can turn nasty, according to one of this summer's top- rating films, My Best Friend's Wedding, starring Julia Roberts, who turns up at her old friend's wedding determined to snaffle the groom and get to the altar herself by hook or by crook.

Old flames are the most likely sources of a dangerous hidden agenda. "I certainly had my own plans when I went to my old boyfriend's wedding. I should have been the one marrying him and I was as flirtatious as I could be," says Anna, 30. "I was so pleased to see that the bride didn't look very glamorous; her arms looked like mottled sausages and she had the most hideous make-up. Nothing came of it, but if he'd turned round before the ceremony and said `Let's get out of here' I'd have gone like a shot."

And then there are the well-meaning but equally maddening: the parents, or future parents-in-law. Because they are forking out, they see it as their day as much as the happy couple's. "When I saw our wedding list, as drawn up by my fiancee's parents, my jaw dropped," recalls Richard, 36. "It was mostly people I'd never even heard of, all their friends - it was as though they were grabbing the chance to have their own wedding all over again. They were paying, so my fiancee thought it was fair enough for them to have quite a lot of say over what went on but my heart just kept sinking and sinking. They even vetoed our choice of flowers for the registry office." By the time the big day came, he says, he was wishing they'd opted for a beach-side ceremony in the tropics with no guests at all. "It was a very strained affair. I felt like a spare part."

Weddings, says agony aunt and Relate counsellor Suzie Hayman, author of You Just Don't Listen (Vermilion pounds 8.99), are an emotional minefield. "Weddings are about families, and it's understandable that a lot of people feel they have a stake. But just because it's understandable, that doesn't mean it's excusable."

The reason why weddings are particularly fraught, she says, is because they are simultaneously a time for beginnings and endings. "It's the ending of childhood and beginning of adulthood for the couple, and it is the official end of other romantic possibilities. For the parents it can signal the beginning of old age, friends can feel it is the ending of a special relationship, siblings that they have been left behind. The whole thing acquires enormous emotional freight."

This, she says, is partly the reason for the "look-at-me, look-at-me" stance of the thunder-stealers. "I honestly think that some people are not consciously aware that they are doing it, and it is down to a lack of self-confidence, a feeling of competitiveness and jealousy. You find it much less in married people, more in people who are with their partners and wish that they could take the same step. And those who flirt at their old flame's wedding are saying, `I had him first and I can get him back any time' . Again it's a way of bolstering low self-esteem."

The classic, she says, are the take-over parents. "I get so many letters about this," says Suzie Hayman. "But for the bride's mother in particular it is the end of an era. It's a ritual that takes their child out of their control, and they want to control that ritual." The best way to deal with runaway mothers, she says, is to give them their head - up to a point. "If the couple can talk it over and say, `As long as we are happy in our relationship we'll let her do it' they can feel good about recognising the feelings behind the behaviour."

As for the thunder-stealer, she admits that there is "not a damn thing to be done - except not let it worry you. What is really important is your private commitment. It might sound soppy," she adds reassuringly, "but if you're in love it doesn't matter what anyone else looks like."