The Irregulars opens, much like any other Sherlock Holmes story, on a mystery. But if you think Sherlock Holmes is the protagonist of Netflix’s new drama, you’d be very wrong.

In actuality, The Irregulars centres around a group of working class teenagers in Victorian London. Sisters Bea (Thaddea Graham) and Jessie (Darci Shaw) have already been through the ringer by the time we are introduced to them. Living in a dingy basement with their best friends Billie (Jojo Macari) and Spike (Mckell David), they’ve come out of the workhouse and are now scrounging for food and rent money.

But something strange is afoot with Jessie. She’s having horrible nightmares. She thinks she’s going mad, like their mother. Bea’s worried too, but as the older sister, tries to act as the grounding force. Then, Bea meets the sinister Dr. Watson, who offers her money in exchange for information.

A wild journey – full of fantasy and the supernatural – ensues. But the show also touches on very real elements of family, romance and friendship, breathing new life into an age-old story.

“I’m a long-time Sherlock Holmes fan,” says Jojo. “Probably around the same time my Dad was reading me those stories, I had a VHS tape called Basil The Great Mouse Detective, which is probably one of the greatest pieces of cinema ever created,” he laughs. “That would be my favourite iteration of the tale.”

“When you grow up British, Sherlock Holmes is a part of your culture,” adds Mckell. “The same way that Harry Potter, or even James Bond is, in a weird way. So doing this job is so great, and a blessing. There’s such a movement with the Sherlock world, and it’s something that is so well respected. For me to come in and be a part of that, is magnificent.”

Harrison Osterfield, known best for his role in Catch-22, plays Leo, a hemophiliac prince who hopes to help the gang and escape his sheltered palace life. He clashes with Billie, who is “the protector” of the Irregulars, over his obvious class difference.

“Considering that Leo is the new face in that group, Billie’s going to have very strong opinions about anyone just turning up,” says Harrison. “We spoke about how they’re different in class – and Tom Bidwell has written some incredible dialogue which makes you think about it yourself. I had never really gone too deep into the class structure before, but reading the script, you’re thinking that there are really important points being made.

“That should be spoken about day-to-day. It was such a privilege to have those scenes where we chat about class and bring it to life onscreen.”

“The thing about The Irregulars is the way the filming is set up, the locations, the costuming and the makeup – you become very immersed in this world,” adds Jojo. “You get inside the headspace of the characters. Obviously off-camera Harrison and I are very close, but we did fall into that discussion. We just worked through it together.

“You look at the gaps of wealth in Victorian London and in current London, you can see the sort of tension that it creates. It’s all around us, you can see it wherever you look. It’s very understandable how that sort of hatred or dislike could be formed, from Billie’s point of view.

“Strangely, that scene where we have the class discussion was actually my audition scene, so I had it going round and round in my head for a long time, and it’s something that really formed the basis of the Billie character.”

While saving London and battling monsters, the characters have to find their own sense of agency within a world where they feel quite powerless.

“All the villains in the series are scary,” Harrison says, “but the great thing about them is that they all come from a very real place, whether that’s grief or loss. Our characters can almost always understand why they’re terrorising the city.”

For Mckell’s part, Spike (who is more than just the plucky comic relief!) embodies the inward emotional journey.
“Spike learns a lot about himself,” Mckell says. “At the start of the show, his idea of life isn’t as mature as it gets by the end. He’s growing from a young boy into a young man.”

“Something that really struck me when I was reading the script is that Bea and Jessie kind of discover this together,” says Liverpool-born Darci Shaw. “As Jessie is going through these nightmares, she’s not keeping it to herself, she’s telling her sister everything, confiding in her.”

Although the two girls are very different – Bea trying her best to hold on to realism while her sister experiences the pull of the supernatural – the girls remain close throughout the series.

“They’ve known each other their whole lives as sisters, and experience everything as one because they are so connected,” she says. “I don’t think Jessie would ever suffer in silence.”

“I love that between them,” adds Thaddea. “And I think they’re both aware of this as something that happened to their Mum, and they’re told that this led to her death. They’re both terrified of that.

“Bea, her entire life, has had to be the strong one. She has this weight on her shoulders that she has to protect her little sister, and she’ll do anything to do that. When Jessie, right at the top of episode one, says, ‘Do you think I’m going mad?’ Bea says ‘No, it’s just a nightmare, it’s nothing more.’ I think Bea senses there’s something else going on, but she’s not going to tell Jessie that, because Jessie is panicking enough. She really tries to ground her sister. You see that strength in Bea, where she knows something’s up but says, ‘We can’t both panic’.”

On top of the supernatural monsters the teens battle, they also have to deal with the ominous and mysterious history surrounding Bea’s new employers, Dr. Watson (Royce Pierreson) and Sherlock Holmes (Henry Lloyd-Hughes).

“I loved all of our Watson/Sherlock back-and-forth,” says Royce. “Building that was really exciting. And playing these damaged, ageing icons was super fun. To see their genius come out, now and again, and then to see that fall away when they’re consumed by whatever demons they’re consumed by, it was brilliant to play that.

“I have a lot of scenes with Bea, and our back-and-forth was really important as well, because Watson builds these barriers and hides behind them. So he lives his existence basically waiting to die for his sins of the past,” he continues. “Bea comes along and keeps needling at it, trying to get inside. It’s a beautiful development of a relationship.”

When we meet Sherlock, he’s addled by his opium addiction. It was important for Henry Lloyd-Hughes to show the contrast between the sleuth in his prime, and when Bea and her friends meet him.

“It’s one of the rare instances where the ideas that I pitched in the audition room made it all the way to the screen,” Henry laughs. “Often things get diluted or you come across obstacles, or someone else looks similar so you have to change things. I have to say, Lucy Sibbick, who did the makeup, and Edward Gibbons who did the costuming, elevated the seed of the ideas that I had. We knew we had a time jump, and that meant we had to do a dramatic shift.”

Henry plays young Sherlock like a steampunk rockstar – all rings, tattoos and slinking sex appeal.

“I was almost thinking about David Bowie in his Thin White Duke era,” says Henry. “Strung out on drugs at the peak of his power and just about to lose his marbles – but still a genius. Almost too much genius to know how to handle.

“We pushed the costuming in that direction, making a very slim silhouette with silk. And then with time passing and all the tragedy that has befallen Sherlock, I had a team of tattoo artists in Hackney who specialise in tattoos with occult references.

“We shaved my head, and the physicality and the costume is completely different. We took some of the original costumes and basically destroyed them – I was wearing threadbare versions. The original iteration of the costumes were svelte, and the versions we see when we meet him are decrepit.”

It’s safe to say that while the teenagers are battling the supernatural monsters, Sherlock and Watson are wrestling with their own inner demons.

“I think that’s going to be the window in for audiences exploring the new-style duo,” Henry says. “Ultimately, these guys are reflecting on their past. In the same way, if you’re a huge Sherlock fan, you have all the previous iterations of Sherlock in your head as you’re coming into the world with these new characters. In a weird way, it’s quite meta.”

•  The Irregulars is on Netflix now.