I feel about the word “runner” the way I felt about “mother” when I’d just had a baby – that it was completely fraudulent. You can’t call yourself a runner until you can run for longer than 90 seconds at a time. But you can’t force yourself out running when you’re not a runner. It’s a puzzler, right?

That’s why I went to see Matt Roberts, a personal trainer so high-end that David Cameron was a client; that’s him you could see in the background of paparazzi shots, looking like a security detail, but actually monitoring the PM’s glute engagement. Roberts is my age and I remember him starting out, when I was at the London Evening Standard and all we talked was his abs, the Atkins diet and Zoë Ball. Anyway, 21 years pass and – wham! – he looks exactly the same and I look like his portrait in the attic, the spirit animal who’s done his ageing for him.

Roberts immediately dispells this shadow of inauthenticity: he insists on everyone calling themselves a runner, because everyone was born to run. He can assess a huge amount just from running alongside me for a minute or two: how long my stride is, how harshly my heels hit the ground, what my posture’s like, how much I’m struggling at what kind of tempo. But before that, we do five minutes that is more like therapy.

“When you feel you can’t go on, is it your legs that are killing you, or your lungs?” he asks. Lungs, hands down. Plainly, if I had stronger glutes, then my technique would be better and that would help. “OK, make each in breath four strides and each out breath the same.” The difference is immediate and striking: I could now run for two whole minutes at a time. Next he advises me to make my stride shorter. “You’re only accelerating if you have contact with the ground.” I was halfway round the park before I figured out what he meant; the shorter your stride, the more often your foot hits the ground, the faster you go. Within reason, obviously.

Roberts is full of useful advice: almost everyone is a heel-striker, but if you aim to hit the ground with the middle of your foot, you’ll put less pressure on your patellar tendon in the long term. Keep your head up and your chest open; hunching forward is inefficient. Stamina work is all intervals (a minute fast, a minute slow); endurance work is all about just trying to run for longer without stopping. You have to do both, Roberts says, before commencing a story about Paula Radcliffe’s training regime. Unfortunately, being asked to use Paula Radcliffe as a role model of any sort exceeds every last ounce of my stamina.

What I learned

To improve your speed, you should be “overloading”, running at a pace that is more than you can reasonably stand, for around five minutes every two days. It’s called overloading and it’s almost unbearable.