When a couple announces their engagement, it's usually a moment of joy and celebration. Champagne corks fly, fathers cry, mothers start making out seating plans and thinking about flowers. But the old cliché about gaining a son or daughter rather than losing one doesn't always work quite so well when the happy couple are the same sex. That was one of the main findings of our study which set out to discover what kinds of considerations face those contemplating entering into a civil partnership. We interviewed 54 same sex couples in 2005, shortly before the law changed. All of them had already held a commitment ceremony of some sort or had in other ways registered their partnerships. So in a sense they were in the vanguard, having already clearly demonstrated their commitment to each other.

And yet even among these very settled couples, telling family and friends of their decision to marry was difficult and sometimes very painful. For some, it was a reopening of old sores – like having to 'come out' all over again. Some families simply wouldn't accept homosexuality at all. More frequently, though, they would tolerate it as long as it was not really mentioned, passing it off as a phase, or thinking of the live-in lover merely as a flatmate. The fact of a legal partnership and a marriage ceremony shattered the pretence.

So some didn't even invite their families to the wedding, either to avoid confrontation or because they did not want to cause distress.

Ella: The reason I didn't invite [parents] was because we were actually getting on quite well, moving forward, all our hard work and they'd moved a long way within their world and we'd moved a long way within our world. I thought if I invite them now it will actually be a slap in the face and it's because things were going well that I knew that it was not the right time to present them with this particular issue.

For others, though, parents were truly overjoyed:

Louise: I just said "Mum, we have decided we are going to get married". I used the word marriage as well and she was like over the moon.

Gillian: Oh yes she's gone out and bought shoes for your dad hasn't she? (laughs).

And for some couples their marriage meant that they entered into a wider extended family, just as heterosexual couples do:

Sally: And I said to your dad "Shall I call you father now?" and he said in all seriousness "Oh yes you should do." I don't know whether they see us any differently or whether, your mum and dad at least, to acknowledge us more.

Where friends were concerned, the couples often faced a rather different kind of disapproval. It wasn't their sexuality that was being questioned – but their political choices. Like the radical feminists who dismiss marriage as a patriarchal institution, some sections of the gay community regard it as similarly oppressive – a dilution of the separateness of gay identity.

From people with these sensibilities, our couples tended to encounter a wary ambivalence rather than outright hostility. Friends would be silent on hearing the news, or would find weak excuses not to come to the ceremony.

Frank: Funnily enough [friend] was not able to come because he was out of the city at the time. But he did say had he been in the city, he would have refused to have come. And another friend made a slightly pointed remark. As in, "Oh, what are you taking heterosexual values for?"

Mostly, though, friends did attend the ceremonies – and everyone we spoke to regarded the occasion with very deep emotions and with the utmost seriousness. Few had gone for flamboyant, camp or ironic weddings because the idea of sending up the ceremony itself was simply inappropriate. Rather like Elton John, who arrived in a sombre suit rather than looking like a latter day Marie Antoinette, our respondents wanted their ceremonies to have gravitas and meaning.

Jackie: Yes, I wore a dress and she wore a suit.

Alex: You are not getting me in a dress, no way!

Jackie: [It was] the quickest shopping for a dress I have ever done in my life, wasn't it? I walked into the first shop and there it was. I did not wear a big thing: I cannot be doing with that.

Alex: No, there were rumours going round the gay scene that we had a horse and carriage and she had a meringue dress and all that crap.

Alex's scorn of the 'meringue dress' sums up the way in which these couples were breaking with tradition, yet retaining the symbolic importance and seriousness of their vows. Interestingly, it was the removal of any religious requirement that paved the way for this legislation – yet 45% of our interviewees claimed some degree of religious faith and wanted to include a religious or spiritual dimension in their ceremony.

And even those who were atheist or agnostic adhered to the idea of a moral commitment.

Lynn: It was just the moral aspect of it that we vowed to each other, didn't we?

Jill: Yes, but it was not religious at all

Lynn: … not in a religious ceremony way

Jill: …morally, because that could be humanistic couldn't it?

The availability of marriage for same sex couple is not only a huge advance for human rights – it has also, perhaps unpredictably, begun to change how they relate to each other and to those around them. But clearly, the most important impact for those we spoke to was that their relationships would at last receive the social and legal recognition they deserved.