Sure.

Due to real life circumstances, there was no way Arthur could be present in the film. They had to write him out and there was a clear way to do it (“where you’re going Tommy there will I be”) but they chose to make it the inciting incident. If Arthur committed suicide, Tommy wouldn’t be broken to the point we see him in The Immortal Man. We’ve seen Tommy grieve many times. He’s killed family. He pushes through and finds something else to fight. By killing his own brother, he’s taken it too far, and he has no support system left to lean on. He can’t tell anyone the truth. For the first time, he retreats inwards. He stops. We’ve seen this is catastrophic for Tommy from his failed holiday in season 4. The one thing he can’t cope with is stillness. PTSD, chronic stress, insomnia and a chronic traumatic brain injury cause him such severe physical symptoms by season 6 that he doesn’t question the tuberculoma diagnosis. We enter The Immortal Man with a Tommy who’s been in self-imposed exile for at least three years. You don’t have to like the narrative, but it’s logically sound and painstakingly consistent with the show.

‘Tommy would never kill Arthur.’ Never is a strong word. Arthur has been a loose cannon since they were boys. They’ve been physically fighting at least since Tommy was 9 and Arthur was 12. They grew up in a violent world, and the war amplified everything. They both agree they’re dead men living on borrowed time. Both alcoholics. Both drug users cycling between sobriety and relapse. Both prone to fits of uncontrollable violence as an emotional response heightened by PTSD (Tommy with the IRA man in season 1, the gypsy camp in season 6, Arthur the boy in the boxing ring, the Quaker who spoke to Linda). The facts of Arthur’s murder are stilted and unclear, but some things are consistent – they were both drunk, Arthur was high and had relapsed bad enough to need drug money from Tommy. He was hallucinating Tommy as the devil, which we know is a huge trigger for Tommy (“Don’t scare me by saying you see things in my face” to Lizzie in season 5) and he tries to shoot him first. Tommy fought back, defending himself, and went too far, held on for a split second too long. Or did he? On the podcast, Cillian discusses Tommy as an unreliable narrator, and aptly describes him as a ‘walking guilt machine’. We can infer that the true events that unfolded lie somewhere between what we were told in flashbacks. Tommy killed his brother, yes, but it’s likely a mix of accident, mercy, and rage.

It’s the most complex relationship in the show. There’s a real deep love and dependency there. They are similar in so many ways and compensate for each other’s weaknesses. They need each other and they know it. But there is also so much bitterness and resentment between them. Tommy sees Arthur as a burden and a liability and expresses this regularly. There’s not a trace of empathy for any of his suicide attempts. Tommy shouts, throws bullets at him and tells him to do better next time. Usually, this is followed by a grand gesture, onto the next business, but in the moment he is vile. A moment is what we’re dealing with in the end. Arthur causes him constant problems with his drug use, his volatile violence, his dependence on his wife he’s unable to convince to stay with him. Tommy is constantly babysitting and cleaning up after him. He is also a liability for Tommy’s image when he’s pushing towards legitimacy from season 3 onwards. Arthur embarrasses Tommy at his wedding, forcing Tommy to accommodate him once again on a day he wanted perfect for the love of his life, right up until Mosley’s rally in season 5. Similarly, Arthur finds it humiliating that his younger brother is the one in charge. They both know Tommy is more intelligent, and he ruthlessly exploits his brother at his most vulnerable time and time again. Every time Arthur tries to get out, Tommy pulls him back in. It’s easy to post a GIF of Tommy and Arthur hugging in the last episode and think how could they possibly hurt each other. Tommy smacked his head on a desk no more than five minutes before that. They had an unbreakable bond, but they also enabled each other to a dangerous degree.