You have to downgrade Fallout 4 to before next-gen version to be able to install Fallout London. You can use a mod to do it, or manually by using the Steam console to ...

Some mods will require you to change the in-game files, install plugins, or even edit scripts. Make sure that you check the mod descriptions before downloading ...

The Fallout series is well-respected as one of the best isometric Western RPGs around. That being said, the franchise didn't reach the levels of popularity it deserved until Bethesda took the reins.