If you were on the deep level tube during July's recent heatwave, then WHAT'S WRONG WITH YOU.
Seriously though, much of the London Underground network is becoming so sweltering (the Central line hit 36°C recently), something's got to be done for the sake of passenger's comfort — safety, even.
While much of the older cut-and-cover lines now have air conditioning, it's not until 2025 that new air conditioned stock starts being rolled out on the Piccadilly line (and from there, we pray the other deep level lines, namely: Bakerloo, Central, Jubilee, Northern, Victoria and Waterloo & City.)
So what's to be done in the meantime?
Enter a state-of-the-art cooling panel — now being trialled by TfL on a disused platform at Holborn station, as part of the TIES Living Lab programme.
The panel works, explains TfL, by circulating cold water around pipes within a curved metal structure to chill it. This then circulates air with an industrial-sized fan, through gaps in the panel's structure, which in turn is cooled.
"The aim of the new cooling panels," says TfL, "is to significantly out-perform the existing platform air handling units."
When the trial's completed at Holborn, the hope is there'll be further trials — this time, where there are actually customers there to benefit from it — at Knightsbridge station. All being well at this stage, Green Park, Holborn, Leicester Square and Piccadilly Circus (all on the Piccadilly line) could also get cooling panels installed, followed by further locations. As with pretty much every TfL announcement these days, though, all the above is 'subject to funding' (Are you reading this The Government?).
And there is one other (major) caveat to this experiment: even if the panels are a rip-roaring success, they'll cool station platforms, rather than than the trains themselves.
For the foreseeable, you're still going to have to resort to fanning yourself with a discarded copy of Metro.