ZombiU Hardcore -- Approach to Tower of London

Dropping down from the tube, head left up the staircase. Loot the two prone zombies and approach the end of the boardwalk and wait a moment for a zombie to climb the ladder -- kill him. Pick up the rifle to the right.

From your vantage point here, you can use the rifle or the crossbow to take out two zombies from here, one that's under the further boardwalk and one that's roaming around on top of it.

TIP: You can use the rifle to take out the radar jammer on the further boardwalk.

IN SIGHT OF THE TOWER
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Climb down the ladder and walk under the second boardwalk; there should be no zombies left alive.

Climb the ladder up to the further boardwalk if you need to loot the dead zombie or take out the radar jammer; otherwise turn left at the corner of the boardwalk, scan up and left to scan the CCTV junction.

Turn right and look across the water from you -- you can see the tower in the background beyond the massive walls and the Traitor's Gate arch. In front of the gate are three zombies roaming around; use your rifle to blow up the bombie and all three will die.

Watch for a moment -- there's a zombie further down that will cry out and he may run up to where the three just blew up. If he does, use the rifle to kill him from where you stand. If he doesn't, cross the water and kill him however you want.

TIP: On the other side of the boat beyond this zombie is a chest with five handgun bullets.

UNDER THE TRAITOR'S GATE
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Enter under the Traitor's Gate -- you can see the C4 location in front of you, but to the right just past the gate is a zombie -- take him out before using the C4.

TIP: Equip your bat and then use the C4, standing far enough back to not get killed but close enough to run through quickly through the newly opened gate as soon as the fire clears. Once through, trip the spitter that's just getting up from laying on the ground and ZR smash him for an easy kill.

Loot the zombie lying on the ground and kill the zombie that's half sitting up on the far side of the courtyard leaning up against the wall by a small arch -- he'll grab as you try to go through the arch if you don't kill him first.

The single wooden door in the courtyard takes you to a now-useless ladder and a manhole back to the Safe House.