When you reach the top of the third ladder, you'll be facing the long ledge where you started the level. Instead of jumping over there, take a standing jump across the gap between the ledges to land on the small, metal ledge below.

Turn left and take a running jump across the alley to land on the roof where the zip line is anchored.

Move to the right end of this roof and carefully drop down onto the little roof with the small medi pack.

Grab the horizontal crevice in the wall and traverse to the right...

...until you can pull up onto a flat ledge. (The angled roof below is safe, but there's no need to drop down.)

Climb up two block steps then turn right...

...and follow the passageway...

...to a gap above the alley with the painter's scaffold. Jump across the gap and continue around the corner.

Kill another crow and then climb onto the ledge ahead.

Pick up the large medi pack and press the button (this is the one you uncovered earlier) to raise the scaffold.

NOTE: If you arrive here before raising the glass cover over the button, you may still be able to proceed. Climb onto the metal ledge above and to the right of the button. Grab the edge of the roof and traverse to the left until Lara is hanging directly above the button. Let go...

...and Lara should drop down inside the glass cover. You should then be able to press the button. As far as I know, this works on all versions of the game.

[Part 2 | Return to the Thames Wharf Walkthrough]