Let me tell you about Abe Welch. He's a hired goon who is now in a hospital. I put him there, after performing a melee takedown on him in Camden Market during a mission in Watch Dogs Legion. It was at this point I decided to save him to my collection of tracked people in the game. A menu screen tells me he hates Dedsec, no surprise after I knocked him out. But, having hacked into the hospital, I can now prioritise his care, which will begin to change his mind on Dedsec. From there, I can help him with the other troubles in his life, like his sister who's being harassed. Eventually, I will have the chance to win Abe Welch to my cause. If all goes well, he'll have gone from being a random enemy goon to my new playable character.

Watch Dogs Legion has no default protagonist. Those rumours about being able to play as any 'NPC' in the game were true—while it takes a little work to recruit each individual to Dedsec, you build up a pool of swappable playable characters. As the Ubisoft E3 conference demo showed, the story will play out with whichever character you chose, voice acted cutscenes and all. There is a major, brave twist to this, however: if that character dies in combat, they are gone forever. Permadeath is now a major part of the Watch Dogs experience. You'll have a chance to surrender to your enemies so that doesn't always happen, but it did happen in my 45-minute demo. I recruited a person, watched her liberate Camden Market from goons (and put Abe Welch in the hospital), then saw her get double crossed and shot dead in front of a massive security force. I was a little bit attached. The game's big idea is working.

It sounds novel, but this system has enormous story-creating potential, and in my first hands-on demo, it's made a dazzling impression. Legion is set in near future London, after Brexit, and in a reality where blue and white collar jobs have been swept away by automation. The city is in a difficult state following riots and bombings. It's a surprisingly bold choice of setting by Ubisoft—and as a Brit familiar with both London and living through the predictable chaos of Brexit, it's weird that something so close to my reality is now the basis of a dystopian setting in a computer game. Your antagonist is a private security company called Albion, though, rather than politicians. London here is a kind of broken neon wonderland, full of brightly-lit futuristic streets, but rife with food banks and protestors. There are eight boroughs of London in the game, and I see Camden and Westminster in this demo.

My first playable character is Ashley, a woman old enough to be your gran who struggles to climb over objects. My goal is to have someone new join the cause. The recruitment phase for Dedsec begins in a pub. In addition to the usual Watch Dogs information on each NPC in the world, you can also see what trait every potential target has. Their generated background ties in to what these traits are: I chose someone with a melee attack boost, but you'll see all kinds of buffs based around the different things you do in Watch Dogs. Recruiting someone is a multi-step process, sped up for this demo, but winning them over essentially involves completing side content to help win them over to the Dedsec cause, with a bar representing their opinion of the group. You'll finally complete an origin mission, which makes them playable.

Once recruited, you can assign them to one of three classes, which offer more detailed flexibility of approach than previous games. Enforcer is a gun-focused class, with a combat roll, sticky mines and explosive rounds. Infiltrator has an AR cloak that briefly makes you invisible, as well as dedicated melee abilities, like a shockwave area of effect attack, and the option to hide bodies with an AR shroud. Hackers, meanwhile, have spider robots and spider turrets, and the robot kind will jump onto the faces of enemies like the Facehugger in Alien to take them out. Each class has its own upgrade tree, and each character individually progresses through them.

You can hack drones in Watch Dogs Legion, too, and with the larger delivery drones flying across London, you can drop things on top of enemies from the sky, and use them to fly your character around. If you're a stealth or non-lethal player, Legion feels well optimised for those playing styles. With five storylines and over 60 missions, there should be plenty of opportunity to experiment until you find the class and character traits you like. And even if you don't care about getting that granular, recruiting an army of pensioners is probably quite fun too.

It's not magic, this NPC recruitment system, but it does offer a very detailed simulation, and it makes Watch Dogs Legion feel like it's genuinely innovating. I ask creative director Clint Hocking how many variations and voice actors there are. "That's a complicated question just by itself. We've recorded 20 different what we call 'narrative personas', and those narrative personas all have their own lines written, so it's not just different voices saying the same stuff. They all have different personalities, perspectives and viewpoints, and those are combined with all the other things, the physical animation archetypes and all of that stuff. But roughly, there's 20 major characterisations across the game." That means your recruits will react differently in cutscenes, and that it's much more than just an appearance swap.

The people you meet have their own schedules, family members, jobs, and homes. "There's a huge simulation. It's not just that we create random characters, they all have their own lives and they all have their needs and wants and opinions about Dedsec, the factions and all of that stuff. So when you interact with that simulation, it's not player-centric. The simulation keeps moving. If you kill someone—you see a man and a wife and you kill the guy's wife—he's not going to go to his appointment with his wife any more, he's going to go to the graveyard instead for a little while. And then after a little time, when he's done his mourning, he'll have a new thing to do in that part of his schedule. He'll have a new friend, or a new problem or whatever. All of it keeps moving forward all the time."

I had a really granular question for Hocking, off the back of the demo. Let's say one of your playable characters gets put in hospital, and you use another character to prioritise their healthcare. Would that improve the opinion of Dedsec to the family of your hospitalised character, and make them potentially easier to recruit? Does it go that far? "It does go that deep, yep. The best way to answer your question is to say once you recruit people into your team, they're not removed from the simulation. They're going to keep walking around the world, living their lives and having their friends and family. And yeah, if one of our operatives gets captured by an enemy who's decided to take revenge, and you go and free them, their family will be positively impacted by you having freed them, just as if it was a character in the world."

Whereas Watch Dogs and its sequel offered a slightly superficial glance at the people in the city surrounding you, here they're the stars, and you're supposed to get invested in them. By adding permadeath, the developers are truly testing your affection for the characters you've recruited. Imagine someone you spent 20 exciting hours with is shot to death then gone forever—it's potentially a lot more devastating than, say, picking one of three characters to die at the end of GTA 5. It could be Ashley, the winning frail old lady who guides spider bots into secured buildings, or it could be Abe Welch, your former goon turned hero. Whoever it is, if Ubisoft successfully pulls this off, it'll feel like the end of a story you've started, with all the payoff that brings.

Ubisoft isn't saying anything about what happens when you play online in Legion, just that singleplayer is the 'springboard' into that experience. Just 45 minutes in this city full of potential heroes has captured my imagination, though, and made me want to test how far the simulation can go. This feels like something I've never seen before in an open world game, and I'll be surprised if I play anything else that surprises and delights me this much at E3 this week.