Why I'm turning my gay wedding into a Channel 4 musical

On Monday 31 March, at 10pm, those watching Channel 4 will witness something rather extraordinary. I can't guarantee they will like it. In fact, I'm pretty sure a fair number of people who see it will be utterly horrified, but no one will be able to say they've seen it before.

The programme is my wedding, which will have been filmed as a television musical on 29 March, the first day it is legal for LGBT people in England and Wales to do something they have been fighting for the right to do for years.

Those reading will probably have already decided what they think. Some will maintain it is the coolest thing they've ever heard. And to those people I say, "Yes we are genuinely getting married" and "Yes, even the registrar, a wonderful woman called Franschene, is singing." There are, in fact, only two sentences in the entire 48-minute ceremony which we are required to speak by law.

From many others, we will hear a parade of clichés. "More car-crash telly!" "Not all gay men like musicals." "Musicals are rubbish." "Why would people want to do something so private and solemn in front of two million viewers?"

So why are we sharing our special moment with the world? It's simple. This isn't a musical about our wedding, this is a musical that we have written together about the importance of 29 March, 2014, which happens to feature our wedding.

But while we cheer, sing, dance and pat ourselves on our enlightened shoulders, it shouldn't be forgotten that gay marriage is only legal in 18 countries across the world. Worse still, being gay is illegal in 70 or more, and is punishable by death in seven. This is a film about hope. If within 50 years, gay people in the UK can go from living in fear of blackmail and jail to being able to celebrate same-sex marriage on primetime television, then there is hope for the LGBT teenagers of Russia, Nigeria, Iran...

There remain a number of misconceptions about gay marriage that have presented themselves since we started on this journey. First, and for another few months, gay marriage remains illegal in Scotland and there are no moves to change the status quo in Northern Ireland, so this remains a celebration in just England and Wales.

Second, and largely because LGBT people in civil partnerships have talked about their "weddings" since 2005, many people in this country assume that gay marriage is already legal. Some even assume that this new law means gay men can now get married in British churches. They can't. Or they can at the enlightened Swiss Church in Covent Garden, but not in a Church of England or Church of Wales church.

So what is new? Equality is new. Civil partnerships were never the same as marriage. They were similar, but different, and that is not the same as equal. So, true legal (almost) UK-wide equality is the victory we'll be celebrating in our film; the final piece in a jigsaw that was started by incredibly brave people so many years ago.

But why a musical? My partner, Nathan, and I have 40 years' combined experience in the professional worlds of music, film and theatre. We met when I was the musical director on Taboo and Nathan was performing in it. (We call Boy George our "fairy, scary godmother" and he will play a part in the wedding). As a composer, I use music to express my most private and intense emotions and can think of no more perfect way to express my love and gratitude to Nathan.

Why on earth would I say vows when I can sing them? When I can accompany them with the chords and beats and suspensions that far more adequately express my love for a man who has been my rock for 12 years? Nathan is a musical theatre performer with a great respect and love for the art form. Music has run through our relationship like a perfect golden thread. I write a song – Nathan will be the first man to hear it. Nathan performs in a show or cabaret – I will sit on the front row.

Over the past 10 years I've travelled the length and breadth of England, making musical films about real people, about people living on roads and in forgotten housing estates. I ask people to be brave enough to sing about their most painful and joyous memories. How on earth can I expect them to do this, if, when offered the chance to step up to the bell myself, I refuse to ring it?

A musical journey into our lives, of course, necessarily features our friends and family. The opening sequence, for example, is a setting of emails that were sent to us when we told loved ones what we were planning. Perhaps unsurprisingly the first thing the viewer will hear in our film, apart from the voice of the narrator Stephen Fry, is a chorus of that familiar acronym, OMG!

Viewers may be surprised to learn that our own mothers have agreed to sing a duet, which has been shot on film to be played during the ceremony. It's an emotional account of how they felt when they discovered that their children were gay and I am remarkably proud of it and of them.

Of course it's a risk, but sometimes you have to light your candle and stagger out into the dark. Nothing like this has ever been seen on television before. It is a true first. The first gay marriage on telly. The first marriage in a musical. The first through-sung documentary. You can say what you like about the piece, but it comes from a place of love. Love for musical theatre, and love for one another.

'Our Gay Wedding: the Musical' is on Monday at 10pm on Channel 4