We make the most foolish promises to ourselves when we're drunk. The process usually starts on a school night drinking session, somewhere between the second pint and the third, at the moment when you decide that you're definitely not just "having a couple".
My favourite promise, usually made when I eventually stumble into a kebab house at 1am like a tramp dressed in a John Lewis suit, is that I'll make up for my indulgences with a "pre-work run". As if twenty minutes wheezing around the park will magically cleanse my arteries - which, incidentally, are hardening faster than Silvio Berlusconi in a nunnery.
So it is that I find myself waking at 6am on a Tuesday, suffering from what appears to be the onset of Ebola. Before I know what's happening I'm dressed and lacing up my trainers. This has never happened before. I surmise that my survival instinct has kicked in and put my body onto auto-pilot. "If you don't do some exercise soon," my brain is saying, "you will die." I elect to leave my brain in control and go on the run.
This, it turns out, is a very bad idea.
The run starts well enough at a gentle saunter. A pretty girl runs past me in the other direction and we even exchange a smiling "good morning". All is well with the world. After a quick jog along the fringes of London's Hampstead Heath, I find myself at the foot of Parliament Hill, a short but steep climb to a glorious, panoramic view of the city.
Incredibly I conquer the hill without so much as breaking a sweat. At the top I slow to bask in the achievement. Next to me is a young Hampstead family who have stopped to take in the view. From their conversation it's clear that it's their little boy's first day at big school. I catch the father's eye and we exchange smiles. It is an idyllic moment.
It is at this point that reality kicks in. With a horrible lurch, I realise that the reason I've been feeling so good is that I'm still steaming drunk. Worse, I'm suddenly feeling very sick indeed. I take a panicked look around for cover. There is nothing, not so much as a pot plant. Before I've decided whether to run for it, it's too late. I bend double and make a horrible, hacking noise like a dying Spaniel. Hampstead family, obviously acutely attuned to what a dying Spaniel sounds like, turn to look at me with alarm.
I look up and see the little boy's face feet from my own. He looks at me quizzically, cocking his head to one side, wondering who this curious cretin from the cheap side of the Heath is. I'm just about to mutter something to the effect of "don't mind me," when my stomach contracts and, unable to hold it in, I vomit everywhere.
The resultant mess is hideous, the smell a concoction of overpriced lager and cheap kebab. The father of the family, with genuine concern, rushes to my side.
"The man's being sick! The man's being sick!" shouts the boy, drawing the attention of two passing runners who stop and wander in our direction. Where, I wonder to myself, is Herod when you need him.
"Are you OK, old chap?" says Hampstead dad, patting my back. I'm pretty bloody far from OK.
I look up for a moment and am aghast to see that one of the approaching runners is the pretty girl from earlier on. She looks at me with a mixture of pity and revulsion. There will be no more smiling good mornings for me. I open my mouth to say something about being absolutely fine but words fail me, mainly on account of their being obstructed by another torrent of vomit.
Worse is to come. Just as I stagger up to insist that I'm fine, another retch wracks my body. My face creases into an inhuman grimace and I spasm, making a noise that wouldn't be out of place in a science fiction film. I can't control my limbs, I can't speak.
The boy, looking straight into my gurning, purple face, is plainly terrified. Until now he didn't know that people like me existed and he was distinctly happier for it. He bursts into wailing floods of tears. In my attempt to exercise I have made a small child cry. I am a shameful, shameful man.
The father isn't patting my back now. He's edging back towards his family, his face a little green. The entire group are staring at me with a combined expression of horror. I wipe my mouth and attempt to proffer an apology but almost immediately realise the futility of the act.
Finally, in a fitting crescendo to the hideousness of the morning, I see the father suppress a gag, but it's too late, now he's going too. His wife turns to him in disgust as the child's wails reach a crescendo. The two jogging girls are looking at me like I've just asked them to club a baby seal to death.
I slowly back away before eventually turning round to trudge back home to shower and get ready for work. The experience, apart from being comfortably the most embarrassing of my life, has taught me a simple but valuable lesson: never keep promises that you make whilst drunk.
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