Ubisoft's Ghost Recon: Wildlands is not just one of 2017's most-anticipated games. It's also one of the most complex games ever made.

This is thanks primarily to a vast, startlingly realistic map depicting a thoroughly believable near-future Bolivia in the grip of narco-wars, populated by a huge array of AI-controlled virtual humans going about their (often nefarious) daily business.

Top that with the ability to play the entire game solo or co-operatively with up to three other people, and it looks very much as though developer Ubisoft Paris deliberately went out of its way to make Ghost Recon: Wildlands' development as tricky a task as possible.

Handily, we managed to grab an interview with Dominic Butler, Wildlands' lead game designer, on a rare visit to London to find out why.

Meeting with us the day after the premiere of Wildlands, the documentary film about narco-wars and Bolivia which Ubisoft commissioned as a companion-piece to the game, he provided great insight into the techniques and attention to detail that are required to make such a complicated videogame.

Ghost Recon: Wildlands is indisputably a departure for the franchise - a mini-reboot if you like. Which extends to the gameplay: it feels more like a Far Cry game with added military rigour than past Ghost Recon games. They were tightly scripted, pretty linear and involved maintaining tight control over AI-powered team-mates. This is not.

Butler, however, argues strongly that it marks a progression from the existing franchise: "It's still very much Ghost Recon, made by Ghost Recon teams," he said.

So, how would he characterise it?

"It's a military shooter, set in a massive and dangerous open world that you can play entirely from beginning to end in solo or in co-op."

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That's a good jump-in point for us to ask: "Why is that different?"

"It's different because we've got that 360-degree approach, because it sets up an interesting narrative and backdrop against this cartel that has moved in and turned the country into a narco-state. It puts the power into the players' hands, to tell their own stories and to express themselves through the gameplay," Butler added.

There's no doubt that Ghost Recon: Wildlands' open-world environment is a key element in the game. The map is huge - the biggest Ubisoft has ever made - but Butler maintains its size isn't its most appealing attribute: "Something we were really happy about, having Bolivia specifically, is that it's so varied in terms of the different environment types and biomes. You have lush jungle rainforests, riverbeds and swamplands, and you've got farmlands, mountains, snowy peaks, mining areas and everything in between.

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"So while we try to keep the missions open and goal-based, to let players experience them the way they want, that environment adds to the challenge. It's a secondary layer, because you can't play the same way in a snowy peak or in a flat desert as you will in a river jungle basin.

"That's because the line of sight is different and the area of effect is different, so it's forcing you to mix it up and try new tactics, to try new vehicles, to try new weapons, to try new tools. And play in different ways with your friends. That's something that's more interesting than just saying it's the biggest."

Perhaps the most radical decision Butler and his colleagues took was to eschew scripting - a mainstay of all previous Ghost Recon games - in which specific player-actions trigger specific AI movements and events. It meant, Butler says, that instead, Ubisoft Paris had to craft a number of systems that determine how the world reacts to what you do in Wildlands as a player: "We wanted from the very beginning to ensure that the players were going to have total freedom of choice to do whatever they wanted, and to complete the missions how they wanted in terms of order within a bigger narrative.

"In order to do that, we couldn't sustain something in a traditional way, where we would maybe set up certain patrols, or a helicopter that would pass just at this moment, because it was something that the designer had conceived - as we had done in previous games.

"I could set a sequence up so that it works when you come down this road, but what happens when a player drives over the hill in a 4x4, or they drop in from a plane by a parachute, or they disable all the electronics with an EMP, so suddenly all your lights don't work anymore? We had to allow for all that: rather than fighting the scripting all the way, we opted instead to heavily invest in the world systems, so that these things would just keep turning and offering their own challenges.

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"Some of those systems interact directly with each other, and some are just offering other layers of challenge for the player. So you have systems like time of day, which is going to affect the NPCs' (non-player characters') agenda, for example.

"You've got the NPCs, you've got civilians, you've got guards - these guys will wake up, they'll go and get food, they will patrol, they'll go to market, they'll do whatever makes sense for them. But they'll also go to sleep at night, so if you go into a camp at night, you'll see a bunch of guys asleep in the dormitories, you'll see spotlights on. So the world changes with time of day.

"You've got things like weather and traffic that can affect things like line of sight, or the way that NPCs are going to react to you. All of those things create a kind of chorus of different systems that allow players to interject when they want. Having those systems that are always running allows us to have a world that is emergent and reactive."

Butler's insistence on endowing Ghost Recon: Wildlands with the freedom to play however you want had implications when it came to designing and fine-tuning the game's AI.

One key aspect, he says, was to keep the missions simple: "I think that's where it all stems from, the idea that we have challenges set up in the world that are as simple in terms of comprehension as, say, 'We have a target that's in a camp and we need to get him, alive, to this rally point so that we can question him.'

"Now, the way that that camp is set up or the way that the environment is set up could be completely different, but also the way that the player approaches that could be completely different. So we have to have an AI that can react - and will react - depending on how the player comes in.

"It will also react differently if you're playing with friends, so that we have to be able to scale up or down depending on whether you're playing solo with AI team-mates, or with two or three friends. Obviously, friends that are communicating well, that are playing together are going to be very smart, and effective, and the AI needs to react to that as well."

One aspect of Ghost Recon: Wildlands that is bound to lead to wildly differing opinions among those familiar with the franchise is the way in which it approaches the AI of your team-mates, should you opt not to play as part of an all-human team. Although you can opt to play with random human team-mates, life is bound to get in the way at times and dictate that you have to strip in some AI team-mates.

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In previous Ghost Recon games, for many players, part of the fun involved ordering your AI-controlled squad-mates around in fine detail, with complete precision. Others found that level of micro-management annoyingly fiddly - and they, at least, will be happy that Wildlands has comprehensively ditched the need to fuss over your team-mates' actions.

Butler argues that Wildlands' drop-in, drop-out co-operative nature is incompatible with Ghost Recon's past approach to team-mate AI: "It's really important that players, as much as possible, have the same experience, can experience all the same content, whether they're playing in solo or co-op, because you don't have a solo progression or co-op progression - you just have your progression.

"In terms of the AI, we wanted to make something that wasn't going to get in the player's way, but still allowed them to strategise, that still allowed them to be effective and feel like a unit.

"So our team-mate AI is watching the way that you play. It's going to offer fire support, of course - that's really basic - but it isn't going to open fire or take out a camp without you being involved. It's going to offer support, but if you're going in loud and heavy, it will follow suit; if you're going in stealthy and doing a lot more recon, it will help you in that. If you're downed in a fight, it will revive you, and you're going to have to look after AI team-mates as well.

"As well as that, we have a command wheel which allows you, with a single button-press, to give very simple orders: we wanted to make sure that you weren't getting into a situation where you were micro-managing them.

"Micro-management in itself is not a problem: it's something that we enjoyed and it's something we did experiment with on this game. But we wanted to be sure that we didn't lose the flow that the players were in, so something in which you stop to micro-manage implies that you have a more static environment, and something without autonomous systems that are moving in real time. In our world, which has things happening in real-time, you have to react.

"So if you're in the middle of planning a very meticulous setup, it can start to be frustrating because you're doing moment-to-moment stuff and the world is going more minute-by-minute."

Past Ghost Recon games also featured some madly futuristic weaponry, such as guns that could shoot round corners, but as far as the weaponry is concerned, although you do get some good gadgetry, it has reverted to a more true-to-life level. Butler explains why: "Ghost Recon Wildlands is set in 2019, so it's very near future, and we looked to modern tech to see what exists and what would exist in the next few years.

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"We wanted to keep it quite modern: a big part of that is because of the narrative that we're telling. But also because we have a world that players can project themselves into: if I gave you a plasma rifle or a pulse rifle, it's a bit hard to understand which one would better for long-range shooting."

Butler picks out the drone as his favourite component of the weapons load-out: "The drone starts out primarily as a recon tool. Every Ghost has a drone: if you're playing with friends, two or three of you can send in drones and recon different areas. But you can also upgrade that drone. For me, this is what I still find myself doing 100 per cent of the time. I love that drone in terms of its versatility.

"You can really play with it in terms of something that's more about offence, with an explosive charge or a noise-maker to draw enemies in a certain direction. You can also use it with an EMP, you can put thermal vision on it, you can put night-vision on it, or make it super-quiet. There are loads of different upgrades and attachments for it, to make it really not just a recon tool but more of a support system."

One gets the impression, talking to Butler, that he and his various teams (Ubisoft Reflections in Newcastle, for example, crafted all the vehicles in Ghost Recon: Wildlands) must feel they have undergone a process akin to giving birth after several years' gestation. But they are undoubtedly fiercely proud of their baby.

And if Wildlands lives up to the uncompromising level of ambition with which Ubisoft Paris approached its development right from the conception stage, it should be a mighty fine game indeed. It will be fascinating to see whether existing Ghost Recon fans take to it with enthusiasm - and whether it will win a new constituency for the franchise