This is a letter I am emailing to MPs of all parties this morning.

Dear Member of Parliament,

Many of you have already decided to support the Equal Marriage Bill. This letter is addressed to those of you who remain undecided or who intend to oppose it.

Back in 2003 I became the first Conservative candidate to have been selected having already told the selectorate I was gay in advance. The very fact that I was the first inevitably led to a lot of media coverage. I remember a few months later being approached by a 22 year old researcher at the Conservative conference. He walked up to me and said “thank you”. I asked “What for?” He said “For making it easier for the rest of us.” I have never forgotten that.

Constantly being referred to in the media as “the openly gay candidate,” didn’t exactly do me any favours, but there was little I could do about it. So I embraced it, knowing that even if my media profile on this and other issues meant I never made it to the House of Commons I could still do something good, and try to influence debates in a number of areas, You now have the opportunity to do something good for your gay constituents – something which will cost no money to the public purse, and something which will bring joy to many.

The debate about equal marriage has been bogged down in a number of misconceptions and prejudices. First of all, it’s about equal marriage, not gay marriage. Marriage is a very conservative institution and one which Conservatives in particular ought to want to share with everyone. It promotes stability in loving relationships, and gives people more choice. But it is also an evolving institution.

Marriage belongs to us as a civil society. It does not just belong to the church, and while religious institutions have just the same right as anyone else to lobby for or against any change, they cannot be allowed to dictate marriage policy to the rest of us.

Over the years the rules on marriage have changed. Registry office weddings were introduced in 1837. The Peter Bone of his day was no doubt against them, accusing the government of the day of undermining the institution of marriage. In 1994 Gyles Brandreth introduced a Private Members Bill to allow weddings to take place in buildings other than churches. The Paul Murphy of his day accused the Major government of undermining the institution of marriage. The Matrimonial Causes Act changed the law to make divorce easier. The Gordon Birtwhistle of his day accused the Heath government of undermining the institution of marriage. In 2004 the Blair Government enabled same sex couple to enter civil partnerships. Well, you can guess what comes next.

The fact is that none of the then opponents of civil partnerships would now vote to repeal that legislation. Within nine years civil partnerships have become an integral part of our society. Even the then opponents of civil partnerships have come to embrace them. David Davis even shed a tear at mine. He insists he had grit in his eye, but…

Tim Loughton and others insist that equal marriage would undermine the institution of marriage, which has traditionally been between a man and a woman. Er, how exactly? How would me marrying my partner John undermine Tim’s marriage to Mrs Loughton? How would Mrs Bone be undermined by the fact that her husband’s gay constituents might be allowed to commit themselves to each other in a civil marriage? None of the opponents of equal marriage have ever been able to explain this. It may be a good soundbite but it’s a bone with no flesh on.

Yesterday 25 Conservative constituency chairmen (all men, I note), delivered a letter to Number 10 outlining the reasons why they felt that equal marriage should be shelved. Their main arguments appeared to be that it would lose the Conservative Party votes. Their votes, and others. The chairmen argued there was no mandate. Wrong. No one seems to have noticed that it was included in the Tory Equalities Manifesto at the last election.

Sometimes political leaders have to lead, rather than follow, and that is what David Cameron has done here. All the polls I have seen show that a majority of the electorate is actually in favour of equal marriage. It is just a vocal section of the Conservative Party which seems to have an issue with it. Making policy based just on party members’ opinions (in any party) is often a mistake. Policy making needs to be much more nuanced than that.

Some also argue that equal marriage threatens religious freedom. Far from it. Religious freedoms have been protected in the legislation. Indeed, a clause in the bill specifically prohibits the Church of England from conducting civil ceremonies in church. Personally, I think that is wholly wrong, and that they should have allowed the Church the freedom to choose, just like other religions will have. But there you go, you can’t win them all. No religious institution – muslim, jewish, hindu, buddhist, Jedi, whatever – can be forced to conduct gay weddings. It’s. Their. Choice. Ah, say the doubters, but the European Court of Human Rights may say something rather different. Wrong. The Bill has been drafted to ensure that can’t happen.

There is one point where I do agree with the doubters. I see no reason why straight people can’t be offered civil partnerships too. Then we really would have proper equal marriage. I suspect someone is drafting an amendment to that effect, and it would stand a very good chance of passing.

In ten year’s time, when we look back on this debate, I suspect there will be very few people who will want to turn the clock back. Equal marriage has been introduced in many other countries, including Catholic Spain and Protestant Holland. So far as I know it has not undermined straight marriage at all.

Each of you will know someone who is gay. A son or daughter. A work colleague. The guy who owns the shop where you buy your morning paper. Your researcher. Can you really justify saying to any of them: “I am happy to vote to deny you the very same privileges and honour of marriage that I , as a straight man or woman enjoy?” Think on that.

Yours Ever

Iain