It's been only a few weeks since Normal People, the television adaptation of Sally Rooney's hugely popular book, hit our screens but already it's become a classic.

The story follows Connell and Marianne – played by Paul Mescal and Daisy Edgar-Jones – from secondary school to college, as a tumultuous but passionate love affair blossoms between them.

Much has been made about the heated encounters between the pair, with them slipping out of this and that, but there's one thing that is never slipped out of: Connell's silver chain. 

The "unexpected breakout star of the show", as Ray D'Arcy said on his show today, has captivated viewers, working almost as a symbol for Connell's sex appeal.

Costume Designer, Lorna Mugan, the woman responsible for choosing every piece of clothing and accessory the enthralling characters wear joined Ray to chat about the significance of the chain, and how it came to play such a role in the show. 

Important questions first: Is it a chain or a necklace? "It's a chain", Mugan says, putting to rest one of the more subtle but nonetheless fervent debates raging since the show hit our screens. 

"The chain is in the novel", she says. "It's one small line. Marianne notices it on Connell and remembers it as something she saw at school. We knew it was there, we didn't think too much about it but Paul picked up on it straight away. After the first fitting, he said, 'can I get that chain?'

"So we quickly went out, got a selection of chains, he picked that and then he put it on and that was it. He had it on for rehearsals, for the shoot. We never saw it again, it was just on him. It was very important to Paul and looking back now, it does jump out a bit!" 

What does the chain mean for the character of Connell? "I suppose Connell doesn't have a lot. He's a very simple guy, so this chain was going to make a statement and, boy, did it." 

The allure of the silver chain is so intense that a fan of the show started an Instagram account sharing photos of the character wearing the chain by the pool, in bed, everywhere really. Its first post was five days ago and it already has over 38,000 followers. 

"We credit him and we blame him for what's happened", she laughed. 

Maybe we're all just starved of interaction these days, and maybe it's been so long since we wore normal clothes that a humble silver chain seems extraordinary. But much of the costuming in film and television carries hints about the characters. Was this intentional for Mugan? 

"I think the world has kind of fallen in love with Connell and Marianne, and this was a little piece of him that people identify with Connell. They empathise with him. They want to wear that badge of honour with him. It's something you couldn't have predicted."

When asked where she bought the chain, Mugan declined to say. "We only have one chain in the world at the moment and it's now with Daisy so I feel that Paul needs his own chain." 

If she were to share where they got the chain, she says, they could be all snapped up from the shops and if the filming team needed another they'd be caught out. "That would be devastating for Paul, I think."

"Paul gifted it to Daisy at the end and then we had to get it back from her for photos and then it got lost. Then I found it in a shoe so I posted it to Daisy, so that's where it is."

It might be a while until you can nab a replica of Connell's chain, but don't worry. She dropped a few clues, at least: the chain costs "way more" than the £14.99 that The Guardian listed in a recent article. "We're not that cheap!"

Listen back to the interview with Ray D'Arcy on RTÉ Radio 1 below: