In Blogging terms this is a first for me. I've never composed a blog on the train from Manchester to London. I've also never been inside 10 Downing Street before either – so it's going to be a day of firsts.
Good form dictates that I should display a degree of detached cynicism about receiving an invitation to a drinks reception inside Number 10 with the Prime Minister.
I ought to be blogging about how it's an elitist activity that I'm only attending after a sophisticated political assessment of the pros and cons. I feel an expectation to be aloof.
But no, dammit, I'll confess: I'm actually quite excited in a good old fashioned, wide-eyed, thoroughly naïve sort of way.
As a lobbying activist there are certain things which I've found myself ticking off on life's shopping list over the years.
Merely visiting the Palace of Westminster was an excitement in the dim distant past.
Gradually I developed a familiarity with the place. I've sat in the galleries of both the House of Lords and House of Commons. I've attended the committee stages of a Parliamentary Bill. Learned about the nooks and crannies where you can catch famous name MPs for a few precious minutes of attention.
I even once managed to get lost – and marvelled at the way nobody challenged me blundering around so long as I had the right sort of pass prominently attached.
Later, as things progressed, I've drunk at the House of Commons bar; quaffed celebratory Champagne on the terrace; had afternoon tea in the Members' Tea Room and waved at familiar faces across the room.
Wider afield, I know my way around Portcullis House – the Spartan premises across the road, full of meeting rooms. Beyond that, there are the MP's overflow offices scattered around "Scotland Yard" – the former home of the Metropolitan Police.
Around the Westminster village I've also been to meetings inside many of the Ministries along Whitehall, up Victoria Street, or beyond:
Richmond House (home of the Department of Health); the Home Office; Education; Ministry of Justice; Department of Trade and Industry; Communities and Local Government.
Through more than a decade of meetings and events, I've noted how I've gone from initial excitement to simple familiarity with each new locale.
Yet there is something about the home of the Prime Minister in Downing Street which seems different.
I did get tantalisingly close once before. In 1997 I was allowed through the gates on Whitehall with a small party of associates to get as far as the doorstep and deliver a 10,000 signature petition to the doorman. Nowadays people just log in to a web site to petition, so perhaps I should count myself lucky.
Yet that opportunity to peek beyond the front door to what lay beyond seeded a need to know more.
Such is the fascination that I clearly remember my excitement one day in the Autumn of 2004 when an envelope arrived from Number 10. My heart leapt. Was this an invitation to drinkies, I wondered?
I opened the envelope eagerly; read the contents; and actually felt disappointed for a moment when it turned out to be the enquiry to check whether I would accept an MBE!
I figured out, of course, that the MBE would mean an opportunity to tick off another sightseeing experience – to enter parts of Buckingham Palace that you don't get to see on the tourist circuit. Yet, bizarrely, I was still just a little bit disappointed.
So today's invitation to a drinks reception to mark the end of another successful LGBT History Month is undeniably special for me. It allows me to collect another first hand experience.
The Prime Minister will be there, of course – just back from his visit to see Barack Obama and addressing both Houses of the US legislature. Maybe I'll get introduced. But (sorry Gordon) that's not the source of my skittish excitement.
No, it's simple. As I walk through the door I'll just be ticking off a long-outstanding ambition on my list. To have a peek inside one of the famous properties in the world.
There. I've confessed. I'm just a wide-eyed tourist on some levels!