Now that we've officially entered 2021, a slew of new shows [1] are on their way. One series we're looking forward to is Channel 4's It's A Sin, a five-part series that depicts the HIV epidemic in London during the 1980s.

In the series's first teaser [2], released this month, we see Ritchie Tozer (played by Olly Alexander from the band Years & Years) giving an impressive monologue about his extreme scepticism about HIV/AIDS. Backed by a jaunty disco beat, he laughingly recaps all of the conspiracy theories about the illness and how vehemently he believes none of it in the early days of the epidemic.

The series is written and created by Russell T Davies (Doctor Who [3] and Years and Years series showrunner) and follows a young group of friends through the joys and heartbreaks through the '80s. When speaking with RadioTimes, Davies explained the story is loosely based on his own experiences as a gay man who was 18 years old in 1981, just like Ritchie.

Davies also spoke about the importance of casting LGBTQI+ actors in LGBTQI+ roles [4]. "I'm not being woke about this ... but I feel strongly that if I cast someone in a story, I am casting them to act as a lover, or an enemy, or someone on drugs or a criminal or a saint ... they are not there to 'act gay' because 'acting gay' is a bunch of codes for a performance. It's about authenticity," he said. "You wouldn't cast someone able-bodied and put them in a wheelchair, you wouldn't black someone up. Authenticity is leading us to joyous places."

It's A Sin will premiere on 22 Jan. at 9 p.m. on Channel 4, and you won't want to miss it. Ahead, get up to speed on the cast, which is stacked with both relative newcomers and veteran actors alike.

Olly Alexander as Ritchie Tozer

Olly Alexander is best known as the frontman for band Years & Years (yep, it confusingly has the same name as Davies' series, Years and Years). While many of his credits are owed to writing or performing songs for soundtracks, Alexander's also had roles in Gulliver's Travels and Skins

Nathaniel Curtis as Ash Mukherjee

Nathaniel Curtis is a newcomer who's joined the cast as Ash, one of Ritchie's closest friends.

Omari Douglas as Roscoe Babatunde

Another newcomer, Omari Douglas, plays 17-year-old Roscoe in It's A Sin, another member of the tight-knit friendship group. According to Channel 4, Roscoe is "a wild, brittle party boy, always on the run".

Lydia West as Jill Baxter

Lydia West (of TV series, Years and Years) plays Jill, a funny and straight-shooting uni student and the glue that holds the friendship group together.

Callum Scott Howells as Colin Morris-Jones

It's A Sin sees Callum Scott Howells debut in the role of Colin, a quiet Welsh boy who becomes an apprentice at Savile Row.

Keeley Hawes as Valerie Tozer

Keely Hawes has had roles in many films and TV series, including Bodyguard [5], Line of Duty [6], and Death at a Funeral. In It's A Sin, Hawes plays Ritchie's mum, Valerie.

Stephen Fry as Arthur Garrison

Stephen Fry [7] needs absolutely no introduction. The legendary actor and writer joins the cast of It's A Sin as MP Arthur Garrison.

Neil Patrick Harris as Henry Coltrane

Neil Patrick Harris [8] famously appeared in long-running American comedy series, How I Met Your Mother [9] and psychological thriller Gone Girl, and now he's joining the cast of It's A Sin as Henry.