So I lied :)
The Ross Bridge is on the southern access road, although once part of the highway. It was built in 1836, at the request of Lt Gov Arthur, and is another design by architect by John Lee Archer (maybe I should add a tag for his creations?). The two men responsible for building it, as both stonemasons and overseers, were highwayman
Daniel Herbert and burglar
James Colbeck. Herbert's name is still well known Colbeck though has faded into relative obscurity, and when he does get a mention, he's often called John. Both did get a pardon a few years latter though.

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