One night 15 years ago journalist Ben Hammersley was on a deadline at the Guardian newspaper, writing a column on internet radio blogs.

He filed the piece and then, just as he was packing up, got a last minute call from the subs desk (the team that give stories a final check).

“They said: ‘We need one more sentence – just to fill the page,'” the British writer says.

“So I wrote something pompous like: ‘And what should we call this new phenomenon – audioblogs? How about podcasts?'”

A few months later Ben received a call from the Oxford English Dictionary.

They said they couldn’t find any earlier citation of the word “podcast” and asked if he had really made it up?

Yes, he had. Podcasts may not have been born that evening – but they had been christened.

A decade and a half later, what had been a motley collection of what Mr Hammersley calls “mostly unlistenable” MP3 recordings has become a global industry.

Podcasts have become the biggest fad in radio since radio.  People are more drawn to radio because it’s uncensored and anyone can do it.  Podcasts are now produced by commercial broadcasters, individuals and companies with no connection to broadcasting. In fact anyone with something to say, and a few pounds to spend on the equipment to say it, can get involved.

The digital audio files are cheap to produce and, thanks to the internet, easy to distribute.

Mr Hammersley says two changes transformed the market – one cultural and one technical.

A technical breakthrough came in 2012 when Apple produced the iPhone podcast app, which proved a popular library system for listeners.

This was followed by a dramatic improvement in inexpensive recording production and editing equipment.

Finally, the development of 4G mobile phone connections and widespread wi-fi meant listeners could browse, download or stream shows whenever they wanted.

The cultural breakthrough came in 2014 with a very specific podcast – Serial, a piece of investigative journalism hosted by Sarah Koenig, narrating a non-fiction story over multiple episodes.

To date, the first and second seasons of the show have had more than 340 million downloads

“Serial changed everything. By the time it got into series two, the advertising space sold out in a day for sums that went into the millions,” Mr Hammersley says.