The Templar with the lantern (Assassin's Creed: Syndicate), update: Mystery solved!
I had previously posted about a mysterious Templar holding a lit lantern in one of the side-streets beyond St Paul's Cathedral:
Mystery solved: it looks like the Templar is tied to memory "A Spot Of Tea" from Sequence 6. As you tail the cart with the smuggled weapons, and it reaches its destination, if you rush a bit, you can see the Templar with the lantern among other templars that are there waiting for the cargo.
It is the same spot as the one in the first screenshot, and the Templar is in the same position. Apparently him being there even outside the memory marks the secret hideout / meeting place for this specific activity, as obviously Twopenny had already been on it, even before we find out about it. Here is a video too:













