If you’ve been watching Channel 4’s brilliant new drama It’s A Sin, you’ve no doubt fallen in love with one of the main characters, Colin Morris-Jones.

We see the young character move from South Wales to London during the 1980s, making new friends and enjoying the lifestyle that comes with living in a big city.

Played by Callum Scott Howells, Colin’s innocence and finding joy in the every day things in life is what made us all warm to him immediately.

Spoilers are ahead for episode three of It’s A Sin, so you have been warned!

It’s the mid-series shock when we learn that Colin has acquired the HIV virus and he starts to suffer from AIDS-related illnesses.

It ultimately leads to his tragic death at the end of episode three, where the audience are left wondering how Colin acquired the virus as he seemingly hadn’t had any love interests in the show.

Show creator Russell T Davies has revealed that this “whodunnit” element of the storyline was one of his biggest doubts when writing the episode, and it took “a lot of nerve” to do so.

“It gets revealed that he was having sex with his landlady’s son all those years ago, which I think there’s something very true in there – there’s a lot of closeted men who will have a sex life and not tell anyone about it,” Russell said during It’s A Sin – After Hours.

“What I worried about was making that ‘whodunnit’ in a show that’s been very sober. I literally sat here at this desk thinking, ‘you can’t do that, you can’t do that, you can’t do that.’

“I did do it. Sometimes you just have to take a deep breath and do these things. I like it now with the end result. I think it closes Colin’s story off beautifully.

“But out of all the things that happen in this show, that is the one I worried about the most.”

It’s A Sin star Callum Scott Howells joins host Kemah Bob for this week’s It’s A Sin – After Hours where he talks about the audience reaction to Colin and his storyline.

They are also joined by Radio 1 DJ Clara Amfo, chairman of the Elton John AIDS Foundation, David Furnish, and Nathaniel  Hall who plays Donald Bassett in the show.

It’s A Sin – After Hours launches weekly after the main show on Channel 4 and is available to watch on Channel 4’s official Instagram and on YouTube.

It’s A Sin airs at 9pm on Fridays on Channel 4, with all five episodes available to stream on All4 now.

Related: It’s A Sin: Lydia West and Jill Nalder discuss the power of allyship during AIDS crisis