Love it or loathe it, there's one thing nobody can deny: Assassin's Creed's cities are incredible. Ever since ACII draped the beauty of renaissance Florence across our screens, the series' locations have been, in and of themselves, works of art.

Revolutionary Paris, the new backdrop to our throat-slicing adventures, is no different. In many ways, it's a nice return to the template that used to make a star of the game's location, before Creed went down the pirate-sim route and turned its settlements into mere stopovers, or mission collection stations.

When you stay still, it's beautiful. Exquisitely detailed, with every surface, strut and outcrop adorned with carvings, statuettes and architectural willy-waving, just like the real Paris. You can't help but be impressed by the sheer unimaginable amount of work that has so obviously gone into the placement of every little piece of stone and marble. It is said that Unity's facsimile of Notre Dame alone, a single landmark in a city that's stuffed with them, took 5,000 man-hours to construct. I don't doubt it.

But let's be honest, you don't buy a knife-crime simulator just to admire the architecture. Ubisoft has talked a good game about re-inventing their flagship series, having built a new engine and scrapped the now all-too-familiar animations and movesets that have made every entry feel exactly the same for seven years. To its credit, many aspects of the Creed experience have been overhauled, to varying degrees.

Chief among the big changes is the combat system, which completely removes the counter kill crutch. It is now impossible to take out a mob of twenty guards with a bit of patience and knowing to smash Triangle when an enemy telegraphs his next strike. In Unity, open combat is dangerous, and best avoided. It encourages you to stalk from the shadows and run like hell when the merde hits the parasol, acting in a way you'd expect a nippy Assassin to. Gone are the days of Ezio, the 15th century Batman-cum-John Cena who never loses a fight and shits stab wounds.

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The movement and free-running controls have been expanded and tinkered with, with a system that's similar to the old one but that now enhances the verticality of the playground, and gives you direct control over whether your guy crouches or not. The latter point addresses an absurdity that was at its most evident in Black Flag, where crouching was automatic and occurred when stepping into thick grass, and cancelled whenever you stepped out, leaving you exposed and easy to spot.

There's now different buttons for climbing up and down, with the idea being that you can scale a building downwards instead of leaping into a fortunately placed bale of hay or repeating the drop-and-hang maneuver until you either reach the ground or die of boredom. With seven-years worth of muscle memory to fight against, the new controls feel horrid and alien at first, but you'll get the hang of it. It never quite felt right, even by the end of a three-hour play session, but I suspect that it'll be fine after a couple of stints. I hope.

The new co-op missions, a central feature of the game's marketing to date, are pretty decent. Taking the form of optional side-tasks on your world map, they come in a few flavours. The two I demoed took the form of a 'steal the painting' heist, where you and three of your mates get to rob a house, and a 'stab the man' mission, a classic Assassin's Creed staple given the 'now you can bring your bloodthirsty pals' treatment.

The heist missions in particular are fantastic. Sneaking around a multi-level building, being careful not to alert the guards and bugger it up for everyone, keeping watch while your mate picks a lock, finally finding the right painting and high-tailing it out of there. It's genuinely thrilling stuff, and might just be the most worthy addition that Unity brings to the Assassin's table.

Talking of side-missions, they've been beefed-up and injected with plot, and are now interesting little story snippets as opposed to blind, context-less stabbing objectives. The world map is dotted with "Paris Stories", which include murder mysteries and investigating thefts. These small distractions, along with the characters and locations that come with them, do a great job of making Pretend Paris feel like a real place. The city isn't just scenery, it's a place where things happen to people. Usually those things are various types of death, but still.

One story has you investigating the deaths of three monks at a local monastery, in a sort of Sherlock Holmes-lite adventure that requires the use of eagle-vision to explore the crime scene for clues, and interviewing witnesses. When all the evidence is collected and reviewed, it's down to you to decide who the culprit is, and it's entirely possible to collar the wrong one. In fairness, though, this is 18th century Europe, so whoever you send down probably deserves it.

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I enjoyed my short time with Unity, and can't wait to jump into its labyrinth of streets and stories. However, a cloud of doubt hangs over the game's ability to run satisfactorily on the next-gen consoles. To go back to a previous paragraph, Assassin's Creed: Unity is beautiful - when you're standing still.

There's still a bit of time to go, and the version we got our hands on could well be several revisions and optimisations old, but Unity's performance issues are concerning. Targeting 900p and 30fps, it sports the same slightly vaselined look as its stable mate, Watch_Dogs, and gets very muddy and choppy in motion. The framerate behaves more erratically than an aristocrat during peasant uprising - obviously it depends on the scene, and the engine seemed to handle quieter streets and interiors without too many issues, but when trying to replicate moments from the trailers, perched up high, looking down on the crowd gathered at Notre Dame, the FPS took a nose dive into the low twenties. This happened a lot, especially during the kind of rooftop chases you can expect to be getting into pretty regularly. We were playing an Xbox One build, but were told that both console versions are the same.

If the final, retail version can overcome these issues, Unity has all the potential to go down in history as the game that reinvigorated Assassin's Creed, steering it on a course away from tired mediocrity and toward genuine greatness. If not, Ubisoft's boast that the next-gen starts here is going to look very ill-advised indeed.

Let's hope the revolution can be televised to an acceptable standard.