Yesterday morning, an envelope slipped through the letter box. It felt like an invitation to something and on the back were the intriguing words “10 Downing Street”.

It turned out to be an invitation from the Prime Minister to a reception to celebrate the LGBT community in the United Kingdom.

Will I be going? You bet I will.

Receiving that invitation made me realise in some small part why I’ll be marching in today’s Glasgow Pride march.

Now, Pride is an emotion that Christians tend to be a little wary of. After all, didn’t our Lady have something to say about scattering the proud in the imagination of their hearts? Surely she wouldn’t be found dead on a gay pride march?

Well, think again. Our Lady will be marching today in the form of a group of folk from St Mary’s, Cathedral. (Notre Dame de Glasgow indeed).

The word “pride” covers a number of things in English these days – some negative and some positive. The proud hearts that Mary was wanting to send on their way were surely those of the haughty and the disdainful. Rather a different crew to those marching from Kelvingrove into town today.

The pride that is celebrated today is a sense of delight in the well-being of one’s self and others. Entirely a different thing, I think.

I’ll go to the Prime Minister’s reception full of pride in many people.

I’m proud of my congregation for continuing to believe that God’s welcome extends not just to people but to all people. I’m proud of the fact that they took a risk and took me on six years ago. I’m proud of the fact that they have lived up to the “open, inclusive welcome” that we advertise, rather audaciously on everything we print. I’m proud that our heritage in this area is built on the achievements of others of long, long ago. I’m proud of the refuge we gave in secret to Gay Switchboard many years ago when their premises were threatened. I’m proud of the fact that when we started to bless gay couples in church a few years ago, every member of the Vestry individually wrote to me supporting that move. I’m proud of having a diverse team of colleagues from the UK, the US and Nigeria. I’m proud of the intense way that people listen to the sermons in St Mary’s – absolutely convinced as a congregation that there is ever more to know. I’m proud of the Vestry’s response to the govenment on the Equal Marriage consultation. Far more nuanced and balanced and hopeful than anything produced by the national Scottish Episcopal Church.

I’m proud too of those who campaign for equality, wellbeing and justice. Proud of the Equality Network, Stonewall, Pride organisers, Gay Men’s Health and all the rest. I’m proud of those who write into the letters pages of the newspapers and those who tweet and blog for a better world. I’m proud of those who work on HIV/AIDS issues including all those represented at World AIDS Day in St Mary’s each year. I’m proud of those who work on refugee and migration issues in my own congregation and far beyond.

I’m intensely proud of the way the Equal Marriage campaign has become mainstream just a few years after my good-hearted friends told me I was wasting my time because it would never happen in my lifetime.

I’m proud when straight friends and allies walk beside me.

I’m particularly proud of my sisters in the clergy who, by and large, have found it easier to walk beside me in these struggles than most of my straight male friends. The goodness of my sisters reminds me that their own struggle is not over; that justice is indivisible. Reminds me of the common goal, that one day, we will walk in a world free from discrimination and prejudice of any kind.

I’m proud of my gay brothers and sisters in other denominations – from the highest of the high to the wee-est of the Frees. I’m proud of Scott Rennie and of Affirmation Scotland who have supported him and so many others in the Church of Scotland. I’m proud of my gay brothers in the Roman Catholic clergy, some of whom I was with recently. We met in secret for fear of the Church. We prayed for a time when all closet doors would be smashed to pieces, starting with those in the Vatican and we prayed for all those who sit in discomfort on ecclesiastical  thrones throughout the world. For those whose struggle is secret – know that it is valuable, and true and holy and that I am proud of you.

And yes, I’m proud to receive the Prime Minister’s invitation to 10 Downing Street. When one brings up LGBT issues in the church one is more likely to be rewarded with a deep sigh rather than anything else. It is nice that someone has noticed the things I do and the people I work with enough to want to include me in that party.

When I was growing up, I was the only gay person in the world. In my younger years, 10 Downing Street was occupied by a Tory Prime Minister who did all she could to keep me isolated, ill-informed and miserable. Together with others, she promoted the iniquitous Clause 28, maintained inequalities in the age of consent and seemed to do everything possible to keep a lid on those working for equality and justice. These days, instead of the law forbidding teachers from giving advice to gay kids in school, many of them come out in school and expect and receive support and respect that my generation couldn’t even dream of.

So, yes Mr Cameron, I’ll accept your invitation. When I turn up to your party, I’ll turn up knowing that the sexuality battles are not over and justice has not yet been won. I’ll also take every chance to remind you and those with whom you work of the many other social justice issues which burn on the hearts of people of goodwill of every faith and none and which I won’t let go of until God’s kingdom comes.

But, I’ll also turn up knowing that for gay, lesbian, bisexual and transgendered folk these days, things have changed and things are changing for the better.

And that’s why I’ll be marching today in Glasgow.

And that’s why I’m proud.