add_edge_to_route(graph, pred, vertex2, route);

    while (pred != vertex1)

    {

        add_edge_to_route(graph, predecessors[pred], pred, route);

        pred = predecessors[pred];

    }

This still leaves duplicate points which may be a bit wasteful but at least it doesn't seem like any steps will be backwards!

Also, I'm a little sad the github issues are gone, they are very convenient and easy to use. Should I report this under the old svn trac issues?