The most reassuring thing about our mammoth hands-on session with Gears of War 2 Act One came right at the end. As mysterious spiritual COG Tai goes toe to toe with a Skorge, the new predator-inspired Locust complete with cool spinning-blade-on-end-of-staff weapon, a Microsoft policeman came over to our test 360 and turned it off. "That's all you're allowed to see, I'm afraid," he said. Sadness overcame us, as well as a burning desire to keep on playing. So what did we do? We jumped onto another console and played through the first act all over again.

This is just what we hoped we'd feel - the core Gears of War two-player co-op gameplay burning just as bright as it did at the end of 2006 when millions of gamers snapped to cover, chainsawed a Locust in half and curb stomped a downed COG in multiplayer for the first time. What a relief - Gears has still got it.

Epic has kept the campaign largely under wraps in the run up to the release of the Xbox 360's biggest game of the year. We've already pumped hours into the multiplayer, including the new five player co-op mode Horde, impressions of which you can see here. But for many gamers it's the campaign that floats their boat. With that in mind we roadie ran our way to a special Cliff Bleszinski hosted Gears 2 preview event in London, grabbed an Xbox 360 pad, hooked up with a fellow gaming hack for some quality co-op, eased into a lovely sofa and jumped in. This isn't going to be pretty.

Gears 2 begins much like Gears 1 ends - with a cut-scene and voice over from that unexplained dominatrix female Locust voice. We see clips of the Pendulum Wars - the original human conflict over Sera's natural resources, and the Locust invasion from underneath the planet's crust. "The humans of Sera continue to march blindly to their doom," she says. We see the Locust fight back - Jacinto, the last bastion of humanity, is now under threat. "Humanity, as always, brought this war upon itself," the female voice says, cryptically. What could she mean?

Fast forward six months from the somewhat anti-climactic end of Gears one to Act One of Gears of War 2, titled 'Tip of the Spear'. It starts with Marcus Fenix sighing: "It never ends" - an early insight into the mental state of Gears' hulking hero. He's standing outside Jacinto Hospital with intel extraordinaire Anya (who looks much better, and slightly different, this time around) and his best friend Dom. The two are discussing a Locust raid at Pomerot Depot, just down the road - evidence that the Horde is closing in. Winter is threatening to set in, but hasn't quite plucked up the courage to do so. A bumbling trainee arrives to join Delta Squad - "Private Ben Carmine, sir!" It's here you're presented with your first left trigger or right trigger choice, much like at the beginning of the first game - train Private Ben Carmine (which triggers the tutorial), or don't (jumps you straight into the action).

Tai, who we mentioned at the top of the preview, makes his entrance. He's a huge, mysterious shaman-esque soldier with a Pacific Island style tattoo on his face. Despite his softly spoken voice, Marcus tells Dom he's super tough. He fought alongside Marcus years ago and will be a staunch ally during the campaign. For us, he comes across as a bit strange - "I like the glow of Locust blood in this light" - speaking in riddles we don't completely understand.

Soon enough the action kicks into gear, and Locust storm the hospital. Having chosen to train Private Carmine, we spend most of our time vaulting and snapping to cover inside the hospital itself, passing by people dying from Rustlung, or Imulsion sickness, cases of which have been increasing ever since Marcus and co dropped the Lightmass bomb on the Locust at the end of the first game. Your first encounter with the Locust is an altogether sneaky affair. From the first floor of the hospital you can see Locust entering in a room below. Luckily for you, they're passing gas canisters that are just begging to be shot. Marcus shouts "Now!", we pop up out of cover, pepper the canisters and boom! Locust bits everywhere.

Marcus and co then fight their way out of the hospital, clearing the building using much the same tactics as anyone who played just five minutes of the first game will be familiar with. Epic has clearly taken an 'if it 'aint broke don't fix it' approach to the cover system from the first game, despite confirming it's implemented an impressive 400 tweaks. And why not? The easy to use pop-in-and-out cover system Epic nailed two years ago is still to be bettered. "We're going to have hands down the best cover system in the business," Cliff confidently predicts. We're not about to argue.

With the hospital cleared Dom takes the opportunity to ask Anya if she's had any luck chasing up a lead on the whereabouts of his missing wife Maria. Anya tells him that a woman matching her description was released from custody a few days ago, which doesn't go down well with the troubled COG. His desperate pursuit of his missing wife is sure to play a central role in the story this time around (a ruffled photograph of Dom and Maria will be included in the Collector's Edition - Cliff Bleszinski, rather disturbingly, keeps one in his wallet).

After clearing the Locust from the surrounding streets, another cut scene kicks in, this time a rousing speech from the Chairman Richard Prescott, who's mobilising the COGs for the last ditch assault on the Locust underneath the planet's crust. "Humanity faces extinction unless we end this war," he says. Hundreds of soldiers cheer.

The nearby town of Landown is where humanity will focus its attack, the crust underneath Jacinto considered too hard to drill through. Marcus, Dom and Carmine meet up with Dizzy, a cowboy hat-wearing ex-Stranded who has joined the army via Operation Lifeboat - ensuring his family will be supported with rations and shelter. Our mission is to escort a convoy of assault derricks - huge vehicles with imposing drills - to Landown, via spiralling mountainous roads flanked by tall forest trees, and protect them from the inevitable Locust attack.

First off Reavers saddle up alongside our rig. We jump on a turret and pepper them with bullets. The Locust swarm and capture a rig - we tear them up as they desperately scramble onboard. With Landown in sight, the Locust unleash a squad of Brumaks - we pump bullet after bullet into the faces of the giant beasts - bits of flesh spewing out, blood everywhere. Waves of Locust troops descend on the convoy, and, right at the last, a Corpser appears from nowhere. It's adrenaline pumping stuff, and action on a scale the first game didn't even begin to approach.

The convoy is brought to a standstill by a new enemy - Tickers. Similar to the Wretches from the first game, Tickers carry bombs on their backs and head straight for you on suicide runs. The bombs will go off if you kill them too close, so the idea is that you take them out from a distance - no chainsaw kills here. Tai meets up with Delta squad at this point, having survived the wrecking of the rig he was riding further back. Now on foot, Delta has a new objective - to head to a monument at the centre of town and dig down into the heart of the Locust.

In the first game players had COG Tags to hunt down in each level, but in Gears 2 there's plenty more bits and bobs to discover, including newspaper clippings, military monuments and personal journals. One we find, from the Jacinto Sentinel Newspaper, details the Locust Horde attack on Landown and the subsequent Winter of Sorrow in a story titled: "Devastation." Another, a COG Letterhead found inside the hospital, is from a Dr. Nicolette Shannon to COG HQ for Military Ops, who is pleading for medical supplies - a request that is "respectfully denied". A monument we discover is in honour of those who served in the Pendulum Wars. These story snippets, which save to your War Journal for future viewing, help to add flavour to the universe - essential given how sparse in plot the first game was.

It's not long before we're bogged down by attacks. Like in the first game, you'll need to find cover and identify useful flanking positions to take out the Locust. But there are subtle differences. You'll now pop out of cover in different, more intelligent ways. Cover itself isn't the safe haven it once was - wood will splinter and concrete walls will crumble from enemy fire. The gore level has been ramped up, however improbable that thought is. Bits of Locust will fly about the place as you Lancer them into oblivion. The new weapon specific melee kills are particularly brutal (the fist pound is already a favourite of ours). And the pacing and variety feels better, too. We've already mentioned the derrick convoy section. Later on in Landown Delta Squad needs to work its way through a pitch black tunnel (some light is provided by Dizzy on board the derrick), all the while fighting off waves of rushing Tickers. As you see the light at the end of the tunnel, and what looks like respite, a Reaver attacks. Good stuff.

While the graphics are markedly improved - there's much more character detail, the environments are less grey and the backgrounds are incredibly impressive - we weren't as blown away as we were when we first played Gears of War 1. This isn't through any fault of Epic - in many ways the studio is a victim of its own success. Nearly two years later Gears is still one of the best-looking titles on the system. Because of this fact, don't expect to be wowed in the same way as you were last time around. While Gears of War 2's graphics are undoubtedly brilliant, it feels a bit like watching The Matrix for the second time - the impact is somewhat dulled.

As we make our way deeper into the abandoned streets of Landown, we're presented with another route choice - we can either take to the rooftops or soldier through the hotel. We take the rooftops, and get our hands on one of Gears of War 2's many new weapons - the Mortar. This extremely powerful weapon can fire exploding shells from what feels like miles away. It needs to be placed onto the ground to be fired, so you won't be able to run and gun with it. From there a targeting reticule shows the distance the shells will reach before exploding down onto your target - it's up to you to judge it correctly. We found the Mortar hard to use at first. From across the street we were trying to hit Locust and help out our co-op buddy, but missed most of the time, either overshooting or coming up short. It's all about judging distance accurately of course, and we expect it won't be long before players are raining pain down on other players from halfway across the map in multiplayer.

Eventually Delta Squad arrives at the Landown graveyard, where dead soldiers from the Pendulum Wars have been buried. It's soon after this section that we're charged with defending the grindlift from a massive Locust assault (and unlock Dizzy as a playable character). As it looks increasingly bad for Delta, Dom makes Marcus promise to look for Maria if something were to happen to him. Marcus, being the good fella he is, agrees - all part of the new Band of Brothers style emotional feel Epic is aiming at for the game.

It's at this point that the Skorge turns up - the incredibly quick and agile Locust that's surely a distant cousin of the Predator - Epic's clearly been brushing up on its Arnie classics before brainstorm meetings. It slices some armour in half with its spinning blade staff before turning its attention to Delta squad. As you prepare to go underground, Tai takes the Skorge head-on to buy the team time, entering into a chainsaw duel with the intimidating monster. It's at this point that our 360 is turned off. What a ride.

Gears of War 2 inevitably feels very Gears of War. Anyone hoping for a revolutionised Gears experience won't find it here. What you can look forward to, however, is a refined experience, and, even though we haven't played the finished game, we can already tell it's going to be a better game. Epic has listened to its fans and taken on board constructive criticism. The campaign is a much more colourful, varied experience. You'll be able to drive a Centaur Tank right up a mountain, and take on a Brumak with it. You'll even get the chance to ride a Reaver. The War Journal will not only provide access to achievements and collectibles, but screenshots too. The story is more fleshed out, and better explained. The two main characters, Marcus and Dom, now have some emotional drive, something sorely lacking in the first game. And it's a longer campaign, too. "I'm not going to tell you how many hours it is," Cliff says. "It's different for every person. But I can confirm it is longer than the first game."

Is it more Gears of War 1.5 than Gears of War 2? This was a feeling we were beginning to subscribe to as we worked our way through the first act for the second time. The pacing is similar - the change up in blockbuster style gameplay as fast-paced as ever. But something changed our mind. And that something was a sneak peak at a later level in the game from none other than Cliff Bleszinski himself.

Marcus and Dom are underground, trying to rendezvous with the rest of Delta Squad. We get our first sighting of a Rock Worm, a new bullet proof beastie which acts as moveable cover and, somewhat surprisingly, as an integral part of a puzzle. Here, one player needs to shoot a special fruit down from the ceiling in order to tease the Rock Worm to move. As it does so, the other player uses it as cover, protecting himself from incessant Locust Troika fire. Expect even more elaborate use of the Rock Worm as cover later on in the finished game.

As our time with Gears of War 2's campaign came to an end, we were left gagging for more. And that's one hell of a reassuring feeling to have. It's a very familiar experience, but undeniably it's a better one. And we've only played through the first act. We'd tell you to get very, very excited for this game, but we've got a funny feeling you already are.

Gears of War 2 is due out exclusively for the Xbox 360 on November 7.