OK this is it.
I'm standing on Regent's Road, Edinburgh, looking downhill to the start line, 26.2 miles before me.
Over 16 weeks of training has gone into this.
I need the toilet, my legs ache and feel heavy, and I think I'm getting a cold. Focus!
Then the rush comes, the push for the start line, with the lone Scots' piper in the distance. Tears start welling up. Where the hell did that come from?! That hasn't happened since Wolves beat Albion at home last season.
It's an amazing experience that I recommend to all. It's a rarified atmosphere - a large group of people all with a common goal, all positive, nervous, encouraging each other.
The first hour is like a dream, ahead of schedule. Yes the wind is very strong but we head for the coast on a dry, overcast day, which is just what I'd hoped for. Before I know it mile 10 has come and gone and I feel fantastic, must be the adrenalin pumping!
There's a constant stream of male runners relieving themselves alongside the route. I thought this was fitting revenge for Rangers' football fans antics in Manchester a few weeks before and duly joined the trend in the grounds of Gosford House.
Soon after it did get rather more gory. On the right there's a woman crying on the ground, looks like her race is over. On the left a guy throwing up very loudly. Then there's a young lad seemingly unconscious on a stretcher going into an ambulance. All these things just about make it into my consciousness.
Then my legs go after around 18 miles. Just eight left then. It's all fallen apart, all ruined. I'm going to have to walk the rest. An old guy who looks like he's trying to mount a horse rather than run goes past me - how can he be faster than me?!
I'm not having this, I'm going to hobble and catch that old timer. Really it's a blur for the next half hour, time is slipping past but gradually I don't mind because I know I'll reach the end even if I'm slowing.
Then 26 miles gone, just 0.2 left, yep I can run this, the crowd is amazing and I feel like a celebrity. There's my Mum! Oh Lord, I think she's going to ask me if I have blisters before I get to the line.
Three hours 52. Two minutes slower than my flat mate's effort in London. This is really bad news!
At the finish line I feel nothing. My first thought thereafter: is this really the end because it doesn't look that convincing? It might be a mirage or cruel conspiracy. Second, it's actually more painful to stop than carry on. It really was like the ministry of funny walks from then on, runners goose stepping, crawling, being carried. But all wearing their medals.
Will I do it again? Don't be daft - never! Well, at that point I say hello to a girl who finished before me in 3.36. She said that was an hour faster than her first marathon 18 months ago.
Actually, I might just have another go.