I'm going from memory, but from a former journalist who described the process of self-censorship went something like this.
- Stage 1. The journalist finds a story, and full of enthusiasm, writes it up and takes it to the editor. The editor quietly explains that the newspaper owner is unsure about publishing the story, and as it involves an old friend or acquaintance of his, and might cause some discomfort or embarrassment, or potential legal challenge, and would cost a lot of money to make the story watertight, the story is quietly left unpublished.
- Stage 2. The journalist finds a story, and before writing it up takes the idea to the editor. Unfortunately due to lack of resources, time or other reasonable sounding excuses, (wouldn't like to upset the advertisers too much, they pay the wages of all these hard working colleagues) the story is not written.
- Stage 3. The journalist finds a story, but doesn't take it to the editor, and the story is not written.
- Stage 4. The journalist stops finding stories.
I've read similar accounts from many journalists. It's a process of soft censorship. You might only encounter stage 1 of the process once, or witness it from another. They soon notice a pattern and internalise it, even if they don't do it deliberately.
This is why groups lobby the editor if they are unhappy with certain coverage (or rumours of coverage). They might go on a charm offensive and flatter the editor to manipulate them, the overt threats are less rarely used.
A notable thing is that it is usually after retirement and reflection, some journalists become aware of process and mention it.
Notice the difference in coverage for ME issues produced by 'local' BBC outlets in contrast to the national organisation? The local organisations are further away and less likely to receive a quiet word from above until too late. The national editor is charmed, helped, rewarded by praise by the SMC.