A man once offered two camels for my hand in marriage. I was making a documentary in the Nubian desert in Sudan when I caught an older gentleman's eye. He made the offer to my male producer, who very kindly suggested he would split the proceeds with me if I agreed. Never one to rush a decision, I went to look at the proffered creatures. I'm no camel expert, but they seemed rather dapper fellows with many miles left in them. In the end, however, I graciously declined and we all had mint tea instead.

I wonder what the world would have made of me if I had suddenly become the wife of a Nubian nomad about whom I knew nothing? He was a man, I was a woman. Did that make it a pleasing union for all concerned? I suspect even the most rabid proponent of "traditional" marriage might think not, but the offer was entirely in keeping with the origins of matrimony. Historically, marriage had nothing to do with love. It was a legal contract and was about alliances, getting the right in-laws and adding to your property. Things have changed. Now marriage is about love, or at least it should be.

I always wanted to get married. I was very drawn to the idea of a partner with whom you went through life, a mate who was always in your corner. It seemed to me rather perfect that you might come home each day to your best friend, the person you loved and who loved you beyond all others, but I grew up suspecting that, for me, such a union was an impossibility.

I don't remember "discovering" I was gay. I never made what some people insist on calling "a lifestyle choice". If it were a choice, then presumably all of us, including heterosexuals, must at some point sit and ponder our selection, but I have never heard it mentioned when my female friends choose to date a man. Being attracted to my own sex was as much part of who I was as being short or blonde or drawn to the library, but I was made to grow up feeling "other". Most books, films – even advertisements – didn't reflect how I felt, and I often watched the world from the outside. I fell in love with a woman, but by now I was already making a career in television so it was, initially, the "love that dare not speak its name". We had three children, and I began to realise that I could not allow them to grow up with a secret. I would not have them ashamed of themselves or their parents. When I came out in September 1994 I was, as far as I know, the only out lesbian in British public life. I was told my career would be over, and almost instantly the death threats came. We were forced into hiding as a section of the more appalling tabloid press fanned the fire of lunatics. My partner and I withstood the onslaught, but eventually the relationship crumbled under the pressure.

After that I never thought I would find "the one". I was single and sad when I invited myself along to a dinner at someone's house. A friend was going to see people I did not know and I asked if I could accompany her. I don't know why. It's not what I do. It was 14 years ago when, on the doorstep of a stranger's house, I first shook hands with Debbie. We both have the same recollection of the moment. It was as if the world disappeared. It was as much like being hit by lightning as I can imagine. Choice did not come into it. I fell in love. It is a universal condition over which none of us has control. Sadly, circumstances would keep us apart for six years, during which time we slowly built an unshakable friendship and the eventually basis for our partnership.

On 29 March, the Marriage (Same-Sex Couples) Act comes into force and now every citizen is free to get married. We can all celebrate whom we choose to love, and Debbie and I will be renewing the vows we took as civil partners on stage at the Royal Festival Hall in London – a public declaration of a personal love in order to share our joy with as many people as possible.

It has been a hard battle to get here, with some curious objections along the way. I recall hearing a religious leader on the radio saying he thought gay people had "enough equality". I had no idea equality was a concept that could be qualified, and I thought about the death threats. The death threats I've received have always had the same thing in common – a belief that the threat is part of God's work, as if he or she is awfully busy so the sender is picking up the slack.

I find the religious arguments hard to follow. A Catholic acquaintance said she opposed gay marriage on the grounds that marriage was for procreation, yet she herself remarried aged 56 when presumably babies were not high on the agenda. I am keen on a spiritual life and have struggled to find a place for my heart in a religious community. I studied the Bible at length when I was at school and was one of the first three people in this country to study Muslim law at university and I was never able to stop being analytical about the texts. Take the Bible, in which the oldest anti-gay chestnut is, perhaps, the story of Sodom and Gomorrah. Here the town of Sodom is said by some to have been destroyed by God as punishment for homosexual behaviour. From my reading of the story, I would say Sodom and Gomorrah is as much about gay people as Jonah and the Whale is a treatise on fishing. I believe the tale has nothing to do with sex but, as Luke in the Bible reports, is actually about inhospitality to strangers.

To me the sin of Sodom is the way that gay people have been, and continue to be, persecuted in the name of religion. The real crime – shunning those who are strange to you – has been repeated every day to gay people across the world.

Let's not forget the end of the story. The story centres on Lot, who has a very bad day in which his town is destroyed and his wife Sarah is turned into a pillar of salt. He must have felt terrible. He heads to the hills with his daughters where he gets drunk (understandable) and then has sex with his girls (less commendable). More fire and brimstone for this despicable sexual act? No. Honestly, not so much as a rumble of thunder. As a lesson in who you should or shouldn't be poking about with, I feel it lacks a little something.

I am not anti-religion. I just think we need to consider how much understanding of the great texts is about interpretation. Let's not forget, for example, how often the Bible was used to condone slavery. I believe the core of all religion is love. That if you believe in a supreme being, then there is an absolute divine command at the heart of that belief to live a life of love.

My kids are all grown up now and fabulous. They are proud of who they are and, I believe, of their parents. Their other mother and I still consider each other family and between us protect our babies as any mum would. Debbie, too, has a child from a previous life who now rough and tumbles with the rest of them in a great big, loving gang.

Things have changed in the 20 years since I came out. Some of it is great. Having two mums seems to be cool in my kids' world. I remember our oldest, Jesse, getting flu at university and both her mothers racing to look after her. As one of us tidied Jesse's room and the other made soup, one of her friends dropped in. He observed the scene and declared "Two mums! Not fair."

As for my career? Was it finished, 20 years ago? Not quite. This week as well as celebrating my love for Debbie, I will also receive an OBE for services to broadcasting. No one could be more surprised and grateful. I can't say being out has always been easy. I am tired of the lazy journalist who, in commenting on a book or a play I have written or a show I have hosted, feels it necessary to mention my being gay or the origins of my children. It's not something heterosexual writers or performers are endlessly subjected to. I don't know why being gay makes commentators feel free to pose questions they would not dream of asking a straight person. No one ever asks a heterosexual performer or writer in an interview, "When did you first realise you were straight?"

This week we can celebrate in the UK, but I am mindful of the work still to be done in the world. The treatment and attitude to gay people in Nigeria, Uganda and Russia, for example, is medieval and shocking. Closer to home, there are, sadly, still those who live in fear. I hope I can live by example and encourage anyone who still lives in the dark closet to open the door, but I can only encourage. It's not for me to say who should or shouldn't be open about their private lives. We all have to tread our own path. I'm just delighted that mine has crossed with Debbie's.

That we ever even met seems a miracle to both of us. She comes from a family in Lancashire where her father worked in a mill. I grew up travelling the world with a foreign correspondent father from Denmark. Is there such a thing as destiny? Who knows, but it feels like it. Debbie and I had only been a couple for two and a half weeks when she proposed and I accepted. We couldn't understand why everyone thought it was too quick, but we laugh about it now. Loneliness is one of the great afflictions of the modern age. How lucky I am to have found what romance novels call "my other half". I remember asking Debbie where she wanted to go for a honeymoon. I think I expected her to say the Maldives or Mustique but without a moment's hesitation she said the Arctic. How utterly splendid and exciting. I knew for certain that I had found who I was looking for. We had a perfect trip.

Marrying Debbie is one of the greatest things that has ever happened in my life. I know it's traditional to have doubts on the big day, but I confess to just one tiny niggle. I am worried that I am never going to get that camel.

• Sandi and Debbie will celebrate the Marriage (Same-Sex Couples) Act when they renew their vows in public at the Royal Festival Hall, London SE1, at 11am on Saturday 29 March. The event is free and anyone wishing to attend needs to book in advance – either at southbankcentre.co.uk or at the Royal Festival Hall ticket desk on Friday or Saturday morning.