Ben was over six foot tall, a romantic and impulsive American from Alabama, bewitched by England: 'It was the country of my dreams. I had built up a unrealistic idea of it based on literature but I had stepped into a dream, and Dick was part of that dream.'

As for Dick, he was handsome and practical, the son of high-achieving Cambridge academics. 'There are moments in your life you remember absolutely, for ever after,' he says, taking up their story. 'And Ben's proposal was one of them. I thought it was wonderful but I also thought how could this possibly be? Ben had no rights to stay in England, no visible means of support, no family.'

Furthermore, Ben was suggesting they live as a couple - two men in the kind of relationship that could land them in prison if discovered by the authorities; the kind that would remain illegal for another 15 years.

Over half a century later, at 9.30am on 21 December 2005 in a brightly lit office in Cambridge, Ben and Dick were one of the first couples in the country to register as civil partners. There was little fuss, no lavish reception or meandering speeches. At their request, no family members were present. Instead, a younger gay couple acted as their witnesses, and Ben and Dick were theirs. Afterwards, all four returned home for lunch and the chance to talk about what the day had meant to them all. 'I never imagined this moment would come,' says Ben, 78. 'I suppose during the early years of the gay movement the idea was floating around, and I thought "Wouldn't it be wonderful?", but I never really believed I would live to see it happen.' Dick, 75, agrees: 'I can still hardly believe it,' he says.

Judging by the media coverage the following day, one might have imagined the only ones to walk up the aisle on 'Pink Wednesday' were Elton John and David Furnish (not forgetting their black and white spaniel Arthur, nipping at their polished heels). However, almost 700 other same-sex couples across Britain also took advantage of the historic new legislation. Over the last month I've followed three of them: Ben and Dick, Mark and Shaun Johnson from Liverpool and Karen Carter and Joanne Ellerington, who live in Blackpool.

On a purely practical level, all have spent their first Christmas together secure in the knowledge that they can now automatically inherit from each other without a will, benefit from their partner's national insurance contributions and pension, be exempt from inheritance tax and treated as a couple for immigration purposes. Nine other European countries already have similar legislation but for the first time in British history privileges which have been the right of any married couple - most poignantly, the right to register a loved one's death and to be automatically consulted about hospital treatment - are now enshrined in law for gay partners, too. In the event that any of them should decide to divorce, they won't be able to until 2007. As with any doomed marriage, they must give the relationship a go for at least a year and expect the same division of assets if it does go wrong.

But talking to these newly hitched couples, it's clear the legislation is as much to do with love and romance as any of the legal small print. 'Civil partnership' might be one of the least sentimental phrases ever concocted, and filling in a form might not readily inspire kisses, champagne toasts and embarrassing bouts of retro dancing, but the ceremonies that took place on 21 December were weddings by any other name. The day symbolised public recognition for hitherto private love stories. There were bonds nurtured despite periods of secrecy, mutually supportive relationships maintained the hard way, without much celebration or acceptance. Until now.

Despite their very different backgrounds, Ben and Dick have lived together for so long that when you speak to them on the phone it is impossible to tell their voices apart. Unconsciously they echo each other's choice of language. Neither is given to overstatement or melodrama. Ben is not exaggerating when he says: 'We have often asked each other what would have happened if we hadn't met? We now believe - no, we know - that neither of us would have survived without the other.'

When they met one icy New Year's Eve in 1951, the attraction was instant, physically and intellectually. Dick: 'We were both reading English, we both liked the same kind of literature, we both had the same leftish politics. We discovered only the other day that neither of us had any idea of where the college sports ground was!' Did he like the look of Ben, too? 'Oh, I thought he was marvellous!' he smiles.' You have to remember that Americans were rarer in Britain then. He seemed terribly glamorous and exotic.'

In 1962 Ben wrote an eloquent and poignant memoir, The Same Language. It describes his childhood growing up in children's homes across America's deep south after the death of his parents, his flinty determination to make something of his life and his subsequent struggle with the Home Office to stay in Britain after winning a scholarship to Oxford. Last month an updated version was published in which Ben reveals what he could not in the Sixties for fear of serious reprisal: his homosexuality and his love for Dick. The two stories, in parallel, dramatically show how society has changed.

'It was an absolute joy to write,' says Ben. 'I can't tell you the sense of release. I wanted our lives put on record. I didn't want the moment to pass and be forgotten. I didn't want the bad things that happened to us happen to anyone else.'

He recalls a time characterised by ignorance and fear: when gay men constantly ran the risk of being arrested; when the police ransacked address books looking for incriminating names. If one of their circle was charged, everyone would club together to raise the money for a solicitor. Dick talks about a friend whose mother reacted with hostility when he told her he was homosexual. A few weeks later he committed suicide. Ben: 'It's very difficult for anybody of a younger generation to picture it - the sheer level of hostility. The view was that gay men should go to prison and never be let out again.'

Dick: 'There were no role models.'

Ben: 'There were men who were rumoured to be gay. But certainly at the beginning you would not know for sure.

Dick: 'There was such a set way of life then - you got married, you had children. Now people might think, why didn't you protest and make a fuss? But you would have lost your job, your flat, your whole life would have collapsed. We were living in a totally hostile world.'

The Seventies began to bring freedoms they could never have imagined but then in the Eighties they were confronted with Aids. They estimate that they lost more than 40 friends. For the last 30 years they've been quietly active in the campaign for gay rights, setting up a branch of Crusaid in Cambridge and becoming father figures of the gay community in the area. 'I believe passionately in the idea of two against the world,' says Ben. 'Gosh, I do.'

They are delighted whenever younger gay friends fall in love, just as they did over 50 years ago.

Will legal recognition alter their relationship? 'I don't think it changes anything between Dick and me,' says Ben carefully. 'But I do think it changes the way we deal with the world and how the world deals with us.' By way of illustration he recounts how he opened the front door to a man delivering a celebratory bouquet of flowers on the afternoon of 21 December. 'He was gruff-looking, with an earring and so on. He asked if they were for somebody's birthday, and I wondered, "Am I going to tell him the truth?" When I explained, he looked genuinely delighted. "The world is a lot more open minded now," he said.'

There is something incredibly touching about these two dignified men, now in their retirement, talking about their love for one another. Ben, who has been dogged by ill health over the last few years, had been terrified that something would go wrong on their 'wedding day'. 'But it was wonderful. I have the sense of taking a deep breath and embarking on a different stage in our lives. This is the beginning of something new.'

So far, only the Western Isles in the Outer Hebrides has refused to hold ceremonies (although legally they must allow couples to register). On the other side of the debate, Janet Taubman, chief registrar in Liverpool, is a fan of the new legislation. 'It is as momentous a change in the law as women getting the vote,' she says. Over the last year, Janet and her colleague Patricia Dobie have toured the country's register offices with a lecture setting the record straight on 'gay weddings': 1. Fellas don't wear frocks, and girls don't all wear dungarees. 2. Not all the guests will be gay/lesbian/transvestites! 3. Check with the couple if they want to kiss. Most will - it's only natural.'

Janet's first civil partnership ceremony on 21 December was between Mark and Shaun Johnson (a couple serendipitously born with the same surname). Along with Janet, 120 guests clambered out of bed before dawn, dressed in posh frocks and pressed suits, and made their way to Liverpool Town Hall for 8am. A local radio reporter, invited along for the day, told listeners: 'I wish you could see what I can. If anything's going to give Elton and David a run for their money, this will.' Mark's mother Brenda wore diamante shoes and a scarlet hat. His 83-year-old grandmother was decked out in her best fur collar. Shaun's sister Elaine opted for show-stopping high heels. The groom and groom wore black frock coats, cream waistcoats and burgundy ties from Moss Bros.

After the 40-minute ceremony guests piled into coaches and headed for the reception at the Devonshire House Hotel: three buffets, two champagne fountains, just the one cake. Keen to take advantage of the new gay wedding market, estimated to be worth £600 million a year, local businesses donated table decorations, buttonhole flowers and bouquets. The party lasted almost 12 hours. Whenever Mark, 37, lost sight of Shaun, 36, he'd delight in saying: 'Has anyone seen my husband?'

Critics complain that the change in the law undermines family values but it was clear that this was a day for celebrating family ties. In fact, it may never have happened without them. The first time Mark's mother asked him if he was gay, he denied it. The second time he didn't dare. He was 21. He remembers coming home to his parents' house in Liverpool one Sunday afternoon and facing the whole clan, sat in a row on the settee: mother, father, sister, brother. 'They were like judge and jury,' he remembers. 'They said, "We need to ask you something." And I thought, "I can't lie. Not any more." ' Mark cried. His mum cried. His sister cried. His dad looked into space. 'But then - I'll never forget it - he stood up. He told me to stand too. I thought, "Oh God, what's going to happen?" But he put his arms around me and said, "Whatever you are, you are still my son."'

What Mark didn't know was that in another part of Liverpool a similar confrontation had taken place. Shaun had known he was gay since he was at school but he had never told a soul, not least his six brothers and sisters. 'If I saw someone gay on television or something I never, ever said anything. Until I was 25, nobody knew.' The irony was that when he did tell his brothers and sisters it turned out they had guessed years before. He chose a trip to Asda to tell his mum, Dot. '"Oh I know!" she said. Just like that. I nearly crashed the car! "Why didn't you say?" I asked her. "It was for you to tell me," she said, and that was it.'

Mark and Shaun Johnson are from backgrounds where people married young and stayed together. Shaun's father died in a house fire when he was only seven but his mother never remarried. 'We were brought up understanding that infidelity was out of the question. That was just a no go. You take the consequences if you do that.'

Shaun first spotted Mark behind the bar in a fashionable Liverpool club 10 years ago. 'I used to look at him and think I bet you've got a girlfriend. He never let on. He would never look or speak to anyone, and I'd never really chatted anybody up. I couldn't do it. I was just too shy.' Five years later, he saw Mark again. 'This time he was with a group of people I knew and I realised he must be gay. I was like, "Oh-My-God!". That was the first time he'd even looked at me or even noticed me.'

For his part, Mark was not interested in dating. 'I'd just come out of a relationship where I'd been hurt badly. I wasn't ready to meet anyone else.' But over the next few months, Shaun, the shy, laidback Johnson, and Mark, the mysterious, heartbroken one, made friends. Eventually, in the time-honoured tradition, one thing led to another.

'Now we're just known as Mark and Shaun,' says Mark. 'People respect us for who we are.' They both work in the hotel and catering business and describe themselves as 'two normal lads'. Mark will go to watch the football some weekends. 'We're not in-your-face, kind of thing,' says Shaun. 'We're not the type to wear sequinned tops.' In fact, the main problem they face when they go out together is women thinking they're straight and men not believing they're gay.

Stonewall, the gay-rights group, estimates that at least half of Britain's same-sex couples will eventually take advantage of the new legislation. Two years ago Mark and Shaun held a commitment ceremony. It was a chance to celebrate their relationship in front of their families but it had no legal standing. A month before 21 December they sent out invitations to what would be their second 'bit of a do'. They read: 'This time it's for real.'

Shaun: 'We use the word "marriage". It's annoying that we can't legally. Maybe in a couple of years things will change and we will be able to use the same language.'

Mark: 'At least now we can stand up with anyone and say, "Yes, we're together and we're proud."'

Shaun: 'Friends says we're husband and husband.'

Mark: 'Hopefully, in time, registrars will say we've got a wedding today, and it won't be "Oh, there's a gay couple" or "There's a straight couple." Both will be the same. If we can start the ball rolling with the family back-up we've got behind us, that's our contribution.'

Fearing, perhaps, a repeat of some of the demonstrations seen in Belfast when the first gay couple 'married', Brighton's police force decided to send a couple of female officers down to the Royal Pavilion in Brighton for Karen Carter and Joanne Ellerington's civil partnership ceremony. They need not have worried. All morning Karen, 41, and Joanne, 31, had been taken on a tour of Brighton, sat in the back of a velvet-lined carriage pulled by two white horses, complete with rainbow coloured feathers in their manes. Down past the seafront, up along the high street, through Kemp Town, where they used to live before they moved to Blackpool. Children cheered from an open-topped bus. Dustbinmen clapped in the middle of their last round before Christmas. One Japanese tourist was so fascinated he will return home with dozens of pictures of an ecstatic-looking lesbian couple he's never actually met, dressed in matching beaded jackets and funky boot-cut trousers over stack-heeled boots.

Admittedly, this was Brighton, a town with a 20 per cent gay community, but nevertheless the response seemed to be unanimous delight. Whenever the carriage came to a halt, wellwishers came forward to shake their hands. 'Don't they look in love?' said one biddy to another. 'About time too,' said her friend. 'Is it your special day today?' they asked, looking genuinely delighted. 'Congratulations!' said another onlooker. 'I'm doing it next month!'

At 2pm on 21 December, the registrar, Debra Reynolds, stood in front of a smattering of guests, including Joanne's father Ron, wielding his video recorder, in the Pavilion's red drawing room: 'Before we progress, if any person here knows of a lawful reason why Karen and Joanne should not enter into a civil partnership, declare it now.' It was one of those moments beloved of soap opera writers and dreaded by any intended couple. Decades of campaigning for a change in the law were somehow compressed into five seconds. Not a word was said. 'They would not dare!' declared Debra, and you rather thought she was right.

Before they swapped rings they read from Jane Eyre. It's a passage written from the point of view of Jane about her beloved Mr Rochester - 'To be together is for us to be at once as free as in solitude, as gay as in company' - but neatly served as a reminder of how language, as well as attitudes, has changed over the last 150 years.

Joanne, who writes children's books, never imagined she'd meet someone, let alone get hitched. She was a bookish teenager who didn't know anyone else who was gay, in literature or in real life. 'I was beginning to think I'd never meet anyone. I didn't think it was possible to fall in love.'

Growing up in provincial Lincolnshire, lesbians seemed as likely as alien landings. 'The only person I knew of was Martina Navratilova, and I remember thinking she's a lot older than me and I don't really relate to her.' She recalls telling her mother she was gay in her early twenties. What did she think? 'She said: "Is that why you wear army boots?" '

Meanwhile, Karen, a DJ, had always known. 'Quietly, in my own mind, I knew it wasn't a phase, it wasn't something I was going to grow out of. I was always aware of my sexuality, and I came out early. When her mother said darkly, 'If I found out you were a lesbian, you'd have to move out', she never really believed her. 'She never accepted it, but at the same time she did support me.' Would she have come to the ceremony if she'd still been alive? 'I think she would have found it difficult to come to terms with. She'd have come to be polite, but I don't know how, in her heart of hearts, she would have taken it.'

The couple fell in love nearly six years ago over a kitchen table in a shared flat.

Joanne: 'I remember telling Karen I was a lesbian.'

Karen: 'I said, "You can't be." '

Joanne: 'I said, "Why ever not? Because I've got long hair?" '

Karen: 'I had to leave the room, I was so amazed. I couldn't believe that someone that nice, that beautiful, could be single and could possibly like me.'

Since then they've barely stopped holding hands, let alone spent a night apart. 'A matching pair', as Joanne's dad Ron says. Two years ago Karen proposed on a blustery Sunday afternoon in Blackpool, where they now live. 'We took a walk along the promenade. I was really nervous because I didn't know what her reaction would be, and she had no inkling I was going to ask her. I just turned to her and said: "Will you marry me?" There wasn't any hesitation. She just beamed.'

'We could have hung on until the summer for better weather but I didn't want to,' reflects Joanne. 'We both wanted to do it as soon as we could. It was an honour to be taking part in a moment of history, and, to tell you the truth, we couldn't wait a second longer.'