What should you expect when you go past your limits? Pain? strobing lights? Ascension to a higher plane? I pretty much anticipate pain, and I guess most of us would. But how about that ascent to somewhere else?

I took a train to Hampton Court last month with the intention of running to Putney, a distance of 25 kilometres, according to the data on the Thames Path website. The weather was perfect, bright but not hot, and after a sharp shower right at the start, not much wind. Now I’ve run 21k a lot and I have a memory of running from Canary Wharf to Mortlake that ended in me tearfully ordering two beers in The Ship Inn because I didn’t think I’d make it back up to the bar for a second time. But 15 or 16 miles? All in one go? Who does that?

Going beyond a limit that is already extreme for you requires a little flexibility of thought and a willingness to accept pain for a while. Three, whole, hours, it turned out to be for me. OK so it wasn’t pain for the entire 180 minutes — 60 minutes of it was even quite enjoyable — but the thing is once the overwhelming desire to stop and catch the bus home kicks in it’s a long wrestle until you reach your goal. I don’t know how you’d do it. For me it was BBC Sounds and podcasts about Rudi and Adi Dassler and the origins of Puma and Adidas shoes. A bit of Alabama Seven waking up this morning and getting themselves a gun (when I REALLY needed some help) and sometimes just padding along listening to my feet crunching on the tow path. Whatever floats your boat, because you will be doing it for yourself when you go beyond your limit.

The first 5k came and went, so far, so Park Run. Then 10k approached and I was in familiar territory. But now after 10k, it’s that third 5k in a half marathon that messes with your head a bit. 10k to 16k is all graft. You’re past the beginning and you’re nowhere near the end. Abandon ye all hope! All you can do is trot on and mind your own business. Ah but now 16k is up and it’s “just another Park Run left” as I’ve heard on more than one organised half marathon. Except it isn’t. Not for you. Not this time. This is where things get knotty. Heading past 21k with all the things that normally hurt hurting you normally and no prospect of a rest for something like half an hour, your world changes a bit. You simply haven’t been here before.

Now everything is new. What’s that pain? Is your breathing normally like that? Oh bloody hell, just how many more people are going to whizz past you before you get to Putney? Familiar landmarks seem strange because you’re seeing them for the first time with 22k of running behind you. Hammersmith Bridge. Harrods. The thought of running on to Putney makes me apprehensive. I hardly dare to think I will have run 25k, pretty much the furthest I’ve ever run (apart from that unpleasantness that ended up with me snivelling in the Ship). The fear fades as I pass the rowing clubs. I’ve done this, although my watch refuses to click over 25k so I have to run a couple of circles outside LooLoos Cafe before I can get a coffee. And now the 25k is up. I can stop.

Am I different now? To be honest I think I am, if only by the smallest amount. I’ve run 25k. I’ve run in a different place even though I’ve run up the Thames a hundred times. I’m no ultra runner. Nothing on earth could entice me to run 50k (or even 42k if I’m honest). I just don’t think I want to run for five or six hours at a stretch, although plenty of (barely) sane people do. But I planned it. I tried it. I made it. Job done. No need to try 26k. Is there?…