My SAS team has stormed the office complex, the hostages are free, a handful of terrorists lie motionless in the corridors. And I am only slightly out of breath.

This Special Forces thing is really not so tough.

Except we shot one of the hostages by mistake, we didn't double check the terrorists were dead or take away their weapons, and hidden in the room we forgot to check another terrorist lies waiting for us.

Body check

In computer games, I've regularly taken out large groups of bad guys single-handedly, but I am rapidly learning that in real life this is very much harder.

Standing in an office building near Aldermaston, Berkshire, four large men in combat boots, all ex-British special forces, are giving me a taste of what it would really be like to be Sam Fisher, a covert agent from a new computer game called Splinter Cell.

Cocked, locked and ready to rock

In the game, Fisher must free two CIA men taken hostage by terrorists in Azerbaijan - mine is to free two actors being "held hostage" by more ex-SAS men posing as terrorists in the abandoned offices.

The first step in the conversion from hardcore computer gamer to covert operative is getting kitted up.

Off come the jeans and loose sweatshirt, on go black overalls, utility belt, a Beretta semi-automatic pistol strapped to the thigh, a Heckler and Koch MP5 sub-machinegun slung round the neck, bullet proof vest, radio with earpiece and mike, black helmet, and gas mask.

This is dressed to kill.

Team work

Now to storm some offices. The talk from my SAS instructors is about bursting into a room and "dominating" it.

Once a pair go through the door - special forces never enter a room alone - they'll have to control that room in an instant, each scanning half of the room in an arc from behind the door to the middle, eliminating any threats with two shots to the centre of the body: bang-bang, bang-bang.

To get control of a whole floor of offices is just as straight forward - on the blackboard at least.

Bravo 1, the first team member, bursts into the first office with Bravo 2 and takes control, while Bravo 3 moves in behind in case one of the first two is shot. Bravo 4 remains in the corridor guarding the door.

Sam Fisher: The star of Splinter Cell

Once the bad guys have been dropped, Bravo 3 shouts "clear", Bravo 4 storms the next room with Bravo 3; Bravo 2 backs up these two while Bravo 1 guards the door, and the whole team rolls down the corridor, storming, shooting and clearing as they go.

But when it's time to put this into practice and start bursting open doors, the first thing that goes through my mind is: nothing.

Adrenaline is pumping, sweat patches are forming under all the gear, and everything I've been taught in the last 20 minutes in the classroom, all the diagrams and movement arrows on the blackboard - it's all gone.

Rush job

Do I open the door or does Bravo 2? When I burst in do I go left or right? Do I release the safety catch on my sub-machine gun now or later? When we move on to the next room do I go before Bravo 1 or after?

No time to think. The trainer shouts go, and I burst in, firing as many shots as we can at the terrorist inside.

In the excitement, I forget to move in to the room and away from the doors (the first place anyone else in the room would shoot), I don't leave enough room for Bravo 3 to move in to back us up, I forget to shout "clear" once the room is secured, and I bump into Bravo 2 as I scramble out to storm the next room.

That my attempt at storming a building was an exercise in utter confusion that in real life would almost certainly have left me and my team-mates dead is hardly surprising.

SAS men practice these moves for months on end until the thousand and one details to think about become second nature. And when they've mastered storming buildings they practice storming boats and aeroplanes until that becomes second nature as well.

At least I can console myself that freeing hostages in computer games isn't so simple either - even for former members of the SAS.

My trainer pronounced Splinter Cell "a good laugh", but with his gaming technique it will take many weeks of practice before he completes Sam Fisher's mission and successfully frees the CIA hostages.