Red Dead Redemption

It's a classic Rockstar moment. The nocturnal calm is shattered by the shrieks of a prostitute bursting out of a saloon as a man chases her down and assaults her in the street. I move swiftly to her aid but, still acquainting myself with the controls, succeed only in kicking her in the face as she writhes helplessly on the ground.

The man flees back inside as the girl scrambles to her feet and away. I give chase to the attacker, drawing a rifle as he cowers behind the bar blind-firing. A moment later I have him clean in my sights by the open backdoor and unload a round. Which sails past his torso, through the door, over the street and into the stomach of a girl 20 yards away, who drops to her knees with a blood-curdling scream. The same girl I'd been trying to save. There are belly laughs and there are belly laughs.

It's one of those sudden, unexpected climaxes of bloody action, tinged with darkly comic absurdity, that have become a trademark of Rockstar's openworld exploits. Pigeonholing Red Dead Redemption as 'GTA Wild West' is a seductively neat but ultimately lazy option, handy for journalists seeking to articulate the concept with a tabloid flourish, but one that undermines what is - if not in essential mechanics and structure - in tone, ambition, scope and potential very much its own beast.

The heritage and influence of Grand Theft Auto are important because through its all-conquering series Rockstar has created then refined a genre, while becoming a master at realising the dramatic potential of the medium.

Red Dead Redemption is, the publisher often states, the fulfilment of a dream that began with picking up the half-finished Revolver from Capcom, acquiring the developer, Angel Studios, and renaming it Rockstar San Diego - to create the great videogame western.

Hands-off demos have impressed the leather chaps off us so far, but earlier this week Rockstar invited us over to its London HQ to climb into the saddle ourselves.

First, though, a Rockstar rep gives us an updated snapshot of the project and a taste of what's in store. We start on a map screen, slowly zooming out for effect to reveal the full scale of the gameworld. The huge expanse of land is bisected by a river, with the Americas to the north and Mexico to the south, split into three distinct territories: New Austin, West Elizabeth and Nuevo Paraiso.

Redemption is the largest openworld game Rockstar has made. Size in itself is not an unalloyed good, as those overwhelmed by the vast San Andreas would testify; but an unexplored, unknown wilderness is the point here. Set at the turn of the 20th century, the tension between the lawless old west and the rapid expansion of government and the rule of law is central both on the narrative and the character of protagonist John Marston, torn between his own outlaw past and second-chance family life.

The proto-FBI Justice Department demands Marston help them bring to justice his former gang. His family threatened with execution, he's left with little option but to comply, loyal only to himself as he works with whomever and whatever it takes to protect his wife and child.