David Attenborough's The Blue Planet II helped my business flourish, says Yorkshire milkman

But he needed the work, so stuck at it - and has seen Knight Dairy in the Rotherham area flourish. He knows exactly why.

"The David Attenborough TV show [The Blue Planet II]. Up until that point there, there was no interest. There was no different interest than there had been for the last 10 years or 12 years or whatever. Not at all. The customers I had were more or less the same customers.

Obviously you had to go and get customers, you know, through either knocking on doors or leaflets or whatever - which you still have to do anyway, or the website - but as soon as The Blue Planet turned up there was a lot more interest, a lot more enquiries on the website, people phoning up about the glass bottle thing, which we'd always been doing anyway, this had never changed.

"We do plastic anyway like every milkman does... but even a lot of people that were having plastic turned to glass as well, customers, regular ones. From there, that was the main trigger."

When the pandemic came and people were stuck at home in lockdown, Mr Knight, who is in his early 50s, "had to take the phone off the hook" because he was inundated with enquiries.

Early into the job, Mr Knight estimates that he increased his round by about 100 calls through marketing and advertising but it wasn't until about 10 years later, when The Blue Planet arrived, that he increased by another 30 to 40, then by another 60 or so during lockdown (about 60 per cent of the latter has kept using his service, he says).

The doorstep milk industry's effect on reversing climate change remains to be seen. But one thing's for sure, customers are rolling back the years in the name of hope.

The original series of The Blue Planet was broadcast 20 years ago after a team of wildlife film-makers made a series on the world’s oceans, the scale of which had not been seen before.

The Blue Planet II aired in 2017, using breakthroughs in marine science and technology to reveal the latest discoveries.

Over the course of more than four years in production, teams mounted 125 expeditions, visited 39 countries, and filmed on every continent and across every ocean.

But it also showed viewers how the ocean is awash with plastics, revealed devastating coral bleaching events of recent years and the profound impacts of warming seas.