“Three. Two. One. MARK”. On my signal, we take aim. Not at an enemy, but at a friend. A friend who's currently driving our armoured truck with its EMP payload along a cliff edge – and starting to flinch. “What are you doing? Hey, cut it out…” Too late. We let rip. Everyone laughs.

Hey, it's not like it sounds. Grand Theft Auto Online's new Heist mode hasn't turned us into mutineers or psychopaths – in fact, quite the opposite – but inspired what GTA does best: unscripted, in-the-moment, farce. We're not raising our weapons, but sat in the back of an armoured truck and exploiting our knowledge of the lesser-known controls to lock into first-person mode and… flip the driver the bird (go into unarmed mode, then tap 'shoot' in first-person). GTA Online's new Heists are packed with Hollywood-style action beats to rival Bourne, 007 or the classic 80s action movies, but it's the shared experience and off-mission goof-balling that evoke emotions to rival any set-piece.

The new Heists mode debuts on March 10th on all major formats (they'll be live for PC launch on April 14th, too), for the dizzying price of free. The update delivers five major Heists, playable in four-player co-op, that take around 2 or 3 hours each to complete subject to your skills and approach. Each heist is split into substantial preparation missions of 20-30 minutes each, similar to story mode heists. The update also gives you new daily objectives (a bit like Destiny), new Versus modes and a raft of new vehicles and equipment, including a VTOL Hydra jet fighter and night vision goggles.

We've played through the third heist, The Humane Labs Heist, over the course of three or hours. It wasn't quite the home experience, with four of us huddled in a LAN-style set-up with monitors side-by-side, but running in normal online conditions and using headsets. Bar the usual loading pauses, it's flawless but we'll have to wait to see how it performs in live tests, of course. GTA Online is *usually* pretty stable, and nothing we saw here gave us cause for alarm.

It's been almost 18 months since Rockstar started talking about online heists, and they've assumed an almost mythical importance to the community. In that respect, there's almost nothing that Rockstar could release that lives up to the expectation, but our snapshot is very promising indeed. There's little, mechanically, you haven't done before in story mode or during online missions – think sniping, parachuting, highway pursuits, escort missions and gung-ho street battles – but it's all impeccably executed, with set-pieces reminiscent of The Ballad of Gay Tony's 007-style, explosive yet diverse, panache. There aren't many publishers that give you 20 hours+ of AAA action for free, after all.

To start a heist, you need to hit rank 12 or above, own a high end apartment and await a call from Lester. A new heist room opens up in your home with the same wipe-board style planner as offline heists. Tap L1 to view the heist map, R1 your crew and assignments. As heist leader, you get to invite three of your friends to join the crew, but need to pay for the operation up-front (circa $60k ish). Don't worry – you get the chance to recoup big money later on, and can assign % cuts to team members before the final mission. It's possible to cut yourself up to 55% of the haul and, cruelly, give under-performing crew members a cheerful 0%. However, they earn cash for each prep mission (circa $12k), with bonuses for good performance, kills etc.

It all sounds very cut-throat, but Heists are a different experience to the winner-takes-all Wild West-feel of regular GTA Online, where every new friend is only a stab or tank-blast away from stealing all your cash and generally being a dick. There's a real incentive to co-operate, like Destiny's Raid missions, and renegades will get their comeuppance. Either way, it's best played with real-life friends, where the incidental moments bring the game to life. The shared adversity really binds you together, and there's an odd joy in lolling around between prep missions, with your characters all soaked in blood.

Most of our highlights were off-the-cuff oddities: like the time I drove a friend's $500k+ Pegassi Zentorno into the sea, just so I could eject from the driver's seat (tapping triangle on the PS4 pad) and roll toward the crew on the beach. He liked that less than me. Or the time we shot an enemy chopper and it tumbled out of the sky… only to land squarely on our escape vehicle. Or when one of our crew hurdled a car park gate just as it started rising, and got flipped 20 feet in the air. Your moments will be different, but duration and replay value aside, online heists provide a new canvas for co-operation, not competition. When you're engaged in a heist, random online nut-bars can't enter your game, which is highly welcome.

For a colourful overview of The Humane Labs Heist, watch the GTAVoclock video above. The best prep missions tend to be stealthier, where you're required to co-ordinate positions and targeting. In one, you need to collect code keys at an agreed drop point. Two of you perform the handover (1x bodyguard, 1x buyer), two on lookout duties (2x snipers) – all assigned pre-mission. Naturally, it all goes wrong, and you're suddenly barking “Left! Three agents! No, right! Stop… SUV!” down the headset and co-ordinating as a team.

In another mission, you need to stealthily enter a lab compound using silenced sniper rifles. You'll feel like an ice-cool SWAT team when two guards drop on your mark… but like circus clowns when an armoured vehicle bursts unexpectedly into view, and you need to take the driver down in seconds to prevent the alarm. Oh, and there's a mission where you need to steal a VTOL Hydra jet (which becomes unlocked for free play) from a heavily-guarded aircraft carrier, where all four of you engage in an aerial duel with a fleet of enemy planes. Without giving too much away, the set-piece is crowned by a soundtrack moment to rival jumping on the bike in Vice City to the opening bars of Billie Jean… but we'll leave that to your imagination.

Apart from being a touch familiar – brilliantly orchestrated, but familiar – the only criticism we can level at heists is that they're a *touch* too easy; certainly for those used to the insane intensity of Destiny's tougher raids. However, the big caveat is that we played with very highly ranked characters (99+) with full weapon complements (Bullpup Rifles, Homing Launchers… the lot) and, critically, two Rockstar employees who knew exactly what they were doing. Even then, we died a fair bit. Your crew only gets two lives to complete each mission, so after your first death, the next crew member to die resets the task for everyone. Handily, checkpoints are sensibly placed and you can tap R2 to quick start within 15-20 seconds or so.

If you're looking for a perversely difficult challenge, however, online heists have got you covered. The Criminal MasterMind Challenges require you to finish every heist in order without losing a single crew life on Hard difficulty mode (we played on normal). One death, and it all starts again… even if you're eight hours in on the final seconds of the last heist. Ouch. On the flip side, the level of co-ordination and tactics required is a huge incentive… not to mention the staggering $10,000,000 prize for pulling if off. There are sub-incentives for other achievements ($100k-$1m), like playing all heists in first-person, completing heist finales for the first time etc. Every heist you complete adds new Versus modes to GTA Online (like Hasta La Vista, a pushbike-versus-truck race in a hoover dam with a fairly obvious movie inspiration, plus fresh ambient activities, like helping Trevor shoot planes from the sky).

So, that's online heists. An 18-months-in-waiting, 15-20 hour+, completely free, huge content expansion that makes you feel not quite ten million dollars. Which is entirely the point. GTA Online might be a ceaseless quest for cash, but despite offering the highest dollar sums, heists aren't about financial gain at all. What you're really going to remember is launching fireworks at hillbillies during mission downtime, or reminiscing about that time you blew a prep mission when your friend reversed his plane into yours on the airfield, after surviving a 15 minute aerial dogfight.

Just keep telling yourself that when your crew fails the Criminal Mastermind Challenge after 30 long hours of agonizing restarts because your sniper put down his pad to scratch his nose. It's about trying – and failing – together. Or, if you really are only playing for the thrill of owning shiny new digital hats and sports cars, just flipping your friends the bird.