Andrew Dixon, central London

At first it’s hard to decide which aspect of the new Nike Free Flyknits is most striking: the groundbreaking design or the fact that you’re expected to pay £130 for what is basically a sock with a sole.

The latest in Nike’s lightweight Free line, which first appeared in 2004, Flyknits are designed to encourage you to run naturally: as if barefoot, but with a cushioned sole for support and protection. The key innovation of this version is the upper, which replaces the separate tongue, eyelets and overlays of conventional running shoes with one piece of knitted (I assume by a huge machine, rather than by a factory full of diligent needle-clackers), elasticated fabric for a second-skin-like fit.

The designers seem to have both recreational runners and trainer collectors in mind as potential buyers, as the shoe most resembles one part Aladdin’s slippers – when off the foot the tightness of the knit curls the toe and heel up – and one part a jumper worn by Sarah Lund in The Killing. A colleague remarked that they looked like “something Hugh Hefner would wear if he took up running”. But, as interesting as the aesthetics are, for a runner the real test is how they would handle the worst that London’s streets could throw at them.

Putting them on on a very humid day was the first challenge – it’s a bit like donning a particularly tight flight sock – but after a bit of wrestling I managed to squeeze in my bare feet. Limpet-like, the shoes felt noticeably tighter than my usual running shoes (I have seven pairs). In action, however, they proved very comfortable thanks to the fabric’s stretch and the fact they are free of potentially irritating interior seams. Cleverly, the fabric has different weaves for different parts of the foot; it’s thicker around the heel for example, while across the top of the foot there are perforations to let the skin breathe (which in my black versions created the tantalising look of a fishnet stocking).

Free Flyknit trainers, £130, Nike

In my first trial run, a five-miler through the mean streets of suburban north London, I was struck by the lightness and flexibility of the Flyknit. The sole is so pliable I could bend it between steps just by pushing down my toes. After a while this, combined with the foot-mirroring shape and fit, made it easy to forget I was wearing shoes at all.

When not training for a race, I usually run four or five times a week, typically five or six miles at a time, with a longer run at the weekend. During the week I tested them, the shoes proved to be equally adept in a quick three-mile road race and during a 10-mile cruise on a gravelled canal towpath.

The Flyknit is admirably stealthy: it doesn’t feel like it’s impeding the way your foot connects with the ground, bar absorbing a bit of impact and stopping broken glass tearing your soles to shreds. My footsteps were quiet, a sign that I was treading lightly rather than crashing down on my heel with each foot strike.

On the down side, the tight fit combined with the summer heat made my feet quite sweaty, and there was a spot of chafed skin on one heel after one run. Subsequently I solved the latter problem by wearing socks, but this ruined the stylistic effect somewhat. And while the long, thin grooves in the sole are essential for flexibility, they are also magnets for debris and small stones, which I ended up prying out of my shoes with a dinner knife.

Ultimately, though, the shoe is more than a sock with a sole: It’s a triumph (albeit an expensive one) of pared-down design, retaining only the things you need for a smooth, efficient run, and jettisoning everything else. It was just a shame I had to betray it with socks.

Copyright The Financial Times Limited 2018. All rights reserved.