Ubisoft has been interested in bringing co-op to Assassin's Creed since the days of Assassin's Creed 2, Unity producer Vincent Pontbriand has revealed, explaining that the developer first created a prototype co-op system for the 360/PS3 game all those years ago.

"We've wanted to do [co-op] for a very long time," Pontbriand told VideoGamer.com last week. "We actually started to prototype it during AC2, a very long time ago. Then we started work on trying to implement online into the engine. The engine wasn't built to allow for that, so what we came up with was the PVP multiplayer that came out with Brotherhood, so it actually came out later than AC2. But it branched out from the AC2 code and became its own separate thing.

"But it just wasn't possible to have a seamless experience [on the previous engine]," Pontbriand continued. "The engine was not made for that. The PVP mode was more self-contained and just a snippet of the experience. Fans and people were starting to ask for co-op, but we had to wait for the right moment, and we had to actually spend a lot of time and energy to re-code the entire engine to suit co-op because what we really wanted was the co-op experience to be a shared experience.

"That's what people were asking for. They're not looking for synchronising opening doors or pulling levers, they wanted to share their AC experience with their friends. In order to do that, you have to support replication for every single system. So for PVP assassination, the only thing we replicated was the position and orientation of other players. But everything else, the crowd for example, was unique to each player's session, it wasn't replicated at all. I could see NPCs that you couldn't see, but it didn't matter for the gameplay at all."

But it does in co-op, Pontbriand explains.

"In order to have an actual shared experience you need to have all the NPCs replicated," he continued, "The state of guards if you're fighting them right now, if you're playing a mission you need to be at the same checkpoint... I mean, all these things. And we had to recode our entire behaviour set in order to optimise it to go through the internet bandwidth, all of these things that the previous engine wasn't made for.

"So... we've wanted to do it for a while, it just took a long time for the pieces to come together."

Assassin's Creed Unity launches on PS4, Xbox One and PC on November 14, introducing 4-player co-op to the series for the very first time. Want to know what Jim thought when he went hands-on with the latest build last week? Head through here for his preview.