Hey, man! You can do anything you wanna do! It’s all in your head. The Power of Positivity. How do you think Shackleton got to the South Pole? (He didn’t – Ed.) (Detail – AB).

In today’s can-do world of magical realism, everything is possible. The only barriers are the ones we erect for ourselves.

I know perfectly respectable club runners who can notch up 3:30 in the London. And instead of throwing up all over the Finish line and limping home to bed for a week, like someone in their right mind might, they’re immediately consumed by dreams of breaking 2:30. It’s unlikely they’ll ever make the Olympics, they will reluctantly concede – but the Commonwealths, now that’s a definite possibility…

Don’t get me wrong – I’m all for positive thinking. After all, wasn’t it me who sat down and wept, three miles into the Jordan Desert Cup, because the sand was chafing my little toe? I learned something important that day: don’t run in deserts.

I learned something else too: that if you sign up for something that is beyond your ability by a truly stupid margin, there’s still a slim statistical chance you could pull it off – if only because of a primitive herd instinct that makes us feel even worse about dropping out than carrying on.

However, these anomalies occur in the realm of running endurance, not speed.  The reason is simple: Endurance derives from brute stubbornness. Mules are terrifically good at it. Me and the mules, we just set our jaws and plod relentlessly on across baking salt flats, up Himalayas, over ice caps. It’s all one to us.
Whereas proper athletes, the living divinities who crack out five-minute miles in marathons and don’t even drop their shorts to defecate, might as well be from another star system. Their muscles are made of different stuff – depleted uranium, very likely – and their central nervous systems include a Pain Off switch.

It doesn’t matter how hard you train, you will never compete with these creatures. And for this you should be thankful. I’ve met them. They are automatons. Dress them up in day clothes and they look queerly unconvincing, like dummies in a shop window.

Ask them a simple question like, what in retrospect do you feel about Blair’s collaboration with the US in invading Iraq, particularly given the growing body of evidence suggesting that the threat of WMDs was invented by the Allies to gain a UN mandate for armed intervention?  The best answer you’ll get is a faint electrical crackling from somewhere deep inside the head module.

You see, if your all-consuming concern is shaving 1/100th of a second off your 10k time, you’re unlikely to be the toast of café society.

And if you still harbour a vocation for running at the elite level, just consider the impact it will have on your lifestyle.

You can put that pint down, for a start. And what’s that on your plate? Pizza? Are you mad? Where’s your Slippery Elm Food and potassium paste? And if you thought Doris was staying over, you can forget it. There’ll be time for all that after the New York next November. Nighty-night, Doris!

The truth is, you lack both the physical constitution and the mental fortitude to be a top runner.

So take my advice. Get real. Kick off your trainers, sprawl on sofa with a can of premium strength lager and watch the recorded highlights of last year’s London marathon. That should take about three minutes.

Then take Doris out for a curry.