I've had two goes so far. First I just ran about like a wally and got killed. Second I went up a tower and started to take some guards out and got so engrossed in doing that, my time ran out. if you stand outside the gate, and take out the nearest ones with a sniper rifle, or a silenced pistol, they dont attack you. then take out the ones in the tower nearest you, climb it, then take out them on all the other towers, and partrolling. move to the next tower, and repeat. after a few goes you will know where they all are and you will be able to do it quicker. after that, get on foot, use some of the rifles and get your arse over to the bit you go in - it will be shut, so use the grate instead. as i said, once you know where most of the guards are you will be fine. just remember you can take them out from a distance, as they cant attack you until they get close to you. Ok I'll give that a try next time. Thanks for that.