Proper noun
Richborough
A settlement in Ash parish and Sandwich parish, Dover district, Kent, England, which includes Richborough Port (OS grid ref TR3361).
Like Lemanis ( Lympne ) and Rutupiae ( Richborough ) Dover was connected by road to Canterbury and Watling Street ; and it became Portus Dubris, a fortified port. Source: Internet
With the Roman invasion, a road network was constructed to connect London to the Channel ports of Dover, Lympne and Richborough. Source: Internet
An alternative explanation might be a sailing from the mouth of the Rhine to Richborough, which would be east to west. Source: Internet