Two months out from release and we still haven't been told anything substantial about the story behind Battlefield 3's campaign, and judging by what executive producer Patrick Bach has to say when we visit DICE to check on the game's progress at the end of August, it may well be kept under wraps most of the way to launch. However, we do have a good sense of what not to expect.

Asked about storytelling by a Rock, Paper, Shotgun competition winner, Bach rules out letting you do anything being too controversial.

"In a game where it's more authentic, when you have a gun in your hand and a child in front of you, what would happen?" he asks rhetorically. "Well, the player would probably shoot that child. We would be the ones to be blamed [for the player's actions]. We have to build our experiences so we don't put the player in experiences where they can do bad things."

In other words, Battlefield 3's campaign may very well tell harrowing stories about the futility of war as it rages across Paris, Tehran, New York and all sorts of other picturesque locations, but if there's anything like Modern Warfare 2's interactive killing spree in a civilian airport, you won't be invited to join in.

Bach is clearly a thoughtful man who cares about the details, but you could argue that he is underestimating his audience a little here. BioShock, for example, doesn't let you shoot children, but it does let you rip their heads open and harvest sea slugs taped to their brain stems. People were willing to accept that because the game offered a very strong contextual framework for that horrible decision.

Either way, Bach certainly isn't underestimating his audience's thirst for polish, wincing whenever he spots a minor scripting blemish or bug during a mostly flawless demonstration of a new single-player level. Operation Guillotine is set at night in Tehran about halfway through the single-player campaign, and it's been selected for this preview because, Bach says, it offers a nice counterpoint to the sun-drenched tank battles we've seen so far.

The Tehran level was so hot off the production level that there aren't even any screenshots yet, but it shows a darker, more atmospheric side to the campaign.

It starts off on top of a hill overlooking the city. Our squad is prone on a rubble-strewn road listening to orders crackling out of a radio in between the loud echoing booms of explosions off in the distance. One of the squaddies moves into a crouch, hovering above a perfect set of soft-edged shadows cast in real time by a nearby street light. The action's taking place on PlayStation 3 again and it looks extremely slick throughout. (There's still no sign of the Xbox 360 version, although we're told "not to worry" about it.)

The objective today is to take control of an apartment complex far below, and within a few seconds the squad rises as one - along with a bunch of previously unseen soldiers to the left and right - and we all advance down the hill at a canter.

Within seconds we come under fire from mortars, which send showers of dirt and fire ripping through the trees and men all around us. At one point a mortar lands close enough to a fellow soldier to lift him off his feet and plant him in the dirt. (Later, Bach tells us that this was a dynamic occurrence rather than a bit of scripted spectacle - your story-specific squad-mates obviously can't die, but your other comrades may not be so fortunate.)

After a hundred or so metres of sprinting and dodging fires and explosions, the group crosses under a highway overpass and forms up in front of a concrete wall covered in graffiti. We set up a mortar and fire illumination rounds up over the apartments, then boost each other over the concrete wall and find ourselves in a little gulley leading down to the edge of a shallow river. Gleaming water washes innocently under street lamps and flashes of tracer fire, which are being spat out of dozens of hard-to-place gun barrels on the opposite bank.