Nobody tells you this about Paris, but the city has a secret second skin. Peel back the croissants and the Instagram archways and the obligatory shuffle past the Louvre, and underneath — if you're lucky enough to be travelling with the right person — something rawer is waiting.

If you've ever switched on Night Mode before bed, bought a pair of amber-tinted blue light glasses, or felt vaguely virtuous for using the "warm" display setting on your phone, you're in good company. The blue light narrative is everywhere. Screens emit blue light. Blue light suppresses melatonin. Melatonin is your sleep hormone. Therefore: screens are destroying your sleep. Buy these glasses. Enable this filter. Problem solved.

It's a tidy story. It's also, increasingly, not supported by the evidence.

The Eiffel Tower, it sparkles after sunset.