This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Life on Mars (2006)
Vic Tyler's story about the two rats he and brother locked in an abandoned fridge as kids.
The psych ward episode, which depicts the effects of lobotomy and all sorts of insanity. To make matters worse, a criminal takes all the patients hostage and locks them in a room. The psych ward functions more as an Arkham Asylum than a place to treat patients.
Either I missed an episode or this is from the US version.
In many ways, it is all about Nightmare Fuel (and supposedly Fetish Fuel) coming to life for Sam. I found the Test Card Girl bloody terrifying even before this show aired...
Even scarier: Season 2, episode 1. That bloody whistling.
Whether you take it as Sam being in a coma or go with the Ashes to Ashes explanation, all the good he does to affect the future from 1973 is completely meaningless.