Hi Phil. I enjoyed reading this. It's tense. Exciting. I like the name Red Line. Makes me think of a line that can't be crossed. But also of being on the edge, like an engine at max revs.
I have few suggestions of pernickety edits.
Why do you say "Picture the scene" at the start? I'd start with the the "Four scumbags...". As a reader, I'm already picturing the scene.
I also think there are a few words you use early on that don't quite fit with the hard-boiled voice: "archetypes" (could be "types"?), "benediction", "indifferent and cruel society".
In the first para you have "good boys" becoming bad men. That's nice. But later on Julian is also a "good boy". I think I know what you mean, but he's a completely different type of good boy, so a different description might be better.
"let's get this dome." Unless the talented who wear helmets are referred to as "domes" this might be a spelling mistake?
I also have a thought about structure. As I said, I enjoyed reading this and I would eagerly turn to the next page, but going by what Jack Jordan said in his recent Jericho webinar maybe you should aim to end on some sort of cliffhanger?
It's interesting you said in your intro that the talented are vulnerable. But I didn't see a hint of Red Line's vulnerability. And he didn't make any comment when the gang revealed they had a mole in the Sweeney. Wouldn't he feel a twinge of doubt at that point?
I have no idea where your plot might head, but if the mole is important, or Red Line has some other problem, might it be a good idea to foreshadow it at the end of the chapter?
Anyway, that's my thoughts. I'm no expert in plot: I've just read some stuff while trying to find a way to make my WIP grip the reader.
Thanks for posting!