The missions: Shoot, drive and steal

As you might have guessed, the first 30 or so missions are a warm up to the main event, introducing you to new game mechanics like using the mobile phone, email and the internet, practising the new cover system in a few low-key stand-offs (one based in a warehouse with your Rasta buddy Litlle Jacob around mission 23 springs to mind) opening up the first three areas of the city - Broker,Bohan and Algonquin (the most impressive, visually) and making early enquiries as to the location of that 'special' someone.

The pacing is largely determined by the order you decide to attempt missions, and this will vary depending on the individual player. During the middle section of the game you'll have up to six contacts on the map - each with story relevance. This is one of the triumphs of GTA IV; always ensuring each of the mission threads carry you deeper into the plot, whether it's doing bank jobs with bickering Irish American brothers the McRearys or smuggling diamonds around in a waste truck for Mafioso Ray Boccino.

Even missions from characters like coke dealer Elizabeta Torres and reformed gangster Manny Escuela, who at first seem to be story deviations, all help in getting you new introductions and establishing your reputation across the cities underworld. The net effect is you're always caught up in a fascinating power struggle between any number of criminal characters, which combined with Niko's own personal motivation creates the most tightly-honed GTA to date.

But you probably wanted to hear about some missions? Well, it would be ruinous to give too much away, but the one we've all been talking about comes about 60 or so missions in and goes under the title Three Leaf Clover. It's a mission of epic proportion combining a botched bank job with a relentless gun battle through the streets and subways of Liberty City and an adrenaline-fuelled getaway across the Algonquin bridge smashing through roadblocks. Complete it and Niko's richer than kings. On a completely different tack, we also enjoyed the first helicopter mission with Little Jacob in which Niko has the pleasure of seeing one of his arch-enemies killed with a rocket launcher to the face while hovering over the Humboldt river.

Then there's a great sniper-based mission with hip-hop gangster Playboy-X which takes place on the construction site surrounding Ground Zero with you high on a skyscraper picking union officials off cranes and scaffolding from a lofty vantage point. There's a great surprise later on when Niko has to commandeer a Triad truck filled with contraband by jumping on the roof and holding on before jumping through the vehicles window and shooting the driver James Bond-style.

GTA IV takes the notion of open-world gameplay up another notch when it comes to variation of tactics used to complete a mission. So always look out for alternative entrances (like the back door of a building), alternative exits (maybe use a service lift?) short cuts not picked up by the SatNav and less obvious ways of killing enemies: like switching off their life-support machine. And no, you'll have to find that one for yourself. This sense of liberation from linearity (that many games try to fudge, badly) is a trademark of GTA and nowhere has it been more effectively achieved than here.

It's not all an easy ride though - some missions are just plain tough. To ease the pain of inevitable failure, Niko receives a text message asking if you would like an instant restart. In cases where the mission begins straight from the marker point this is literally an instant retry. However, it's not always that way. For example: in one mission you have to visit a house to get some information from a laptop computer and then receive instructions from your taskmaster on the mobile phone. If you fail the mission you have to do that bit again. And receive the same call. We did this mission three times. And heard the same call three times. Annoying when we already knew exactly where he was going to send us.

It's difficult to see how Rockstar can ever avoid the frustration factor inherent in restarting missions without messing with the fabric of the game, but it did lead to some cursing and silent shaking of the head when we realised we still had to go and buy all our weapons again as well as repeat the preliminary stages of a mission before we could attempt the bit we failed first (or second) time around. The one area that has been improved in this respect is that any character dialogue that occurs in a mission is different each time you play it, often giving you new insight into a character. So there's an argument to say failing gleans you new information, but we don't think you'll be thinking that as you're taxiing back to the gun shop for the third time in a row