Break out your Yao Gui-leather top hats and make some Nuka Cola-infused tea! The newly-announced mod Fallout: London uses the Fallout 4 engine to create a Fallout game set in 2237 (between Fallout 1 and 2, 50 years before Fallout 4) that gives us a look at what's happened to our neighbor across the pond.
Fallout: London will be a DLC-sized mod for Fallout 4 and takes place in a new world with a new protagonist. The reveal trailer, posted yesterday, starts off with a nod to Fallout 3's reveal trailer as the camera zooms out from a wrecked bus as Vera Lynn's We'll Meet Again (a 1939 British song synonymous with World War II) plays. The rest of the trailer features a narrator (voiced by Ciaran Saward) who talks about how buggered London is and how its people are tired of "hearing the Gentry's orders" from behind their security walls. We also get brief introductions to some of the factions vying for control of the city, such as the Last Vagabonds, the fascist Fifth Column, and the Camelot Knights, who are themed around the Knights of the Round Table.
In the trailer's description, the creators write that going for a foreign setting lets them explore "totally new cultures which have not homogenized with their American counterparts." This new setting also lets them explore Europe's history pre-war and how the Resource Wars affected pre-war Britain's class structured society. However, a big question players may have is what series staples can we expect to see in Fallout: London. FEV never reached London, so don't expect any Super Mutants or Deathclaws. As for Vault-Tec and its mascot Vault Boy, they're an entirely American company, so they'll have no presence in London. However, there will be a British counterpart to Vault Boy, and there is something similar to a Vault, but it's more of an underground shelter, so don't expect Better Living, Underground.
The base game, Fallout 4, can be found on Steam and a variety of other platforms. As for Fallout: London, it's PC-only and there's no word on when it will release, but you can find its official site here.