Today I find myself very confused by the Streetmap of the area and the Google Maps satellite view of the area. It should be clear from the route of the water on those links that the pointers are in fact in the same position. The Google link makes it clear that the pub lies to the east of the branch of the water that's marked in purple on Streetmap, which means that it lies to the east of the red line that marks the boundary between postal districts N17 (to the west) and E17 (to the east).
But the pub's postcode is N17 9NG. Huh?
Edit: my "huh?" is at Streetmap. Normally Streetmap is pedantic about postcode boundaries; what I would have expected was for the red line to have diverted around the pub, as happens in lots of other places.
 If the link to the Ferry Boat Inn doesn't work it's because RGL has scheduled downtime this afternoon.