I considered going down to the end of this engineering bit behind the Harbourmaster's office, but I know it's a dead end and I don't think the woman walking her dog did. It felt like it would be a bit weird to follow someone down a dead end, so maybe I'll go back another day. On the other hand, I don't think it counts as a public road..
GPS Coordinates:
51.44612, -2.61709
Location: Spike Island