Fallout: London's project lead has confirmed that the massive mod will need to downgrade your copy of Fallout 4 to a version from before the next-gen updates that dropped earlier this year in order for you to be able to play it. The reason cited is that the next-gen version of Bethesda's RPG "isn't stable enough".
If you're out of the loop, Fallout: London's a full conversion mod for Fallout 4 that's set to let us explore a post-apocalytic version of the English capital, complete with fresh factions and quests. After Fallout 4's next-gen update forced its creators to abandon their planned release date of April 23, the mod has been left in what's felt like a bit of a purgatory.
However, at the weekend, the team behind Fallout: London released a statement revealing that the mod is now undergoing QA testing by GOG.com, the storefront that'll be disrtibuting it, and is therefore just "waiting for the final green light". One detail mentioned in this statement is that the mod not only has its own installer, but also a downgrader, and project lead Dean 'Prilladog' Carter has now revealed that the latter certainly isn't just being chucked in there as a cool optional inclusion, as you might have assumed.