Assassin's Creed Syndicate
The best Assassin's Creed game in years, Syndicate tells the tale of twins Evie and Jacob Frye as they come to London and attempt to wrest control of the city not just from the gangs, but also the series' antagonists, the Templars.
Again, it's a hideously inaccurate version of London, Whitechapel is squatting over Kings Cross, a decision made by the team so it could sell Jack the Ripper DLC, because one of London's most horrifying serial killers is clearly ripe for DLC (so ripe that with Ubisoft's forthcoming Watch Dogs 2, there's a pre-order bonus where you get to bust the Zodiac Killer. Nice.) Still, outside of the griping, most of the highlights of Victorian era London are all present and correct for you to climb all over.
You roam around the city taking part in activities and slaughtering enemy gang members while working your way through the game's main storyline and changing at will between Evie and Jacob. Jacob, being male, obviously is the strong brawler, while Evie is the more delicate, stealthier character. Both have different weapons they're skilled with, but Evie definitely has the edge both in terms of skill choices and kill animations, but also because there's a few missions where she flirts with Alexander Graham Bell and he gets all hot and bothered about it.
Another game taking severe artistic license with London, Zombi is nevertheless an exceptional tale of a Zombie apocalypse in ol' Blighty. This version of the end of the world starts, bizarrely, in Shadwell station.
While initially it launched on the WiiU (as ZombiU) and nearly vanished without a trace, Ubisoft has since brought it to PC and all next-gen consoles. It's good fun, and one of the scarier renditions of the dead walking the earth because guns are fairly scarce and it's not really ideal to try to fight off a flesh-eating monster with a cricket bat.
Part of the fun of Zombi is exploring famous London landmarks like London Bridge or Buckingham Palace and seeing its occupants as zombies before bashing their heads in. Nothing else short of a Zombi sequel is going to offer that, so get stuck in.
Fallen London is a text-based MMO, where your character explores this alternate history version of Victorian London where hell's denizens have their own embassy, people with the faces of squid walk the streets, and things are definitely going bump in the night.
Some of the best videogame writers around have contributed stories to Fallen London, and most of them are available for people to play for free, although you can subscribe to get your sweaty mitts on plenty more.
Don't make the mistake of thinking that because the game is oft-ridiculous it doesn't take itself seriously enough; the world is whimsical, but entirely committed to the act. The result is a great way to spend half an hour a day without spending a penny.