They’re often overlooked by passers-by – but this doesn’t mean they’re not of vital importance. South Yorkshire Fire and Rescue has taken to social media to reveal the mystery behind the yellow H symbols on lampposts.

In a TikTok video the fire brigade explained: “You’ve walked past these small yellow signs your whole life but it was today you realised, finally, after all these years, they are there to tell firefighters where the hydrants are.”

These markings also appear on drain covers and…