It’s a sunny afternoon in Greenwich, and I'm listening to a 22-year-old unravelling the curious world of Korean pop band - and certified international phenomenon - BTS. And it’s already getting complicated.

‘It’s a support system,’ explains Hind, one of an ocean of young men and women feverishly congregating outside the London’s O2. ‘And it spreads a lovely message around the world.’

For the uninitiated, BTS are seven fresh-faced all-singing all-dancing boys from South Korea who are slowly taking over the world. In May this year the group’s album Love Yourself: Tear became the first K-Pop release to break the UK top 40 and shot to the top of the Billboard charts in the US.

In August, 43.2 million people watched their single Idol’s music video in its first 24 hours on YouTube, smashing the record previously held by Taylor Swift.

But, arguably, it’s their fans, known collectively as ARMY (standing for Adorable Representative M.C for Youth), that really set BTS apart from your standard plastic-packed UK/US boy band.