How did the Romans plan their great road to the north, Dere Street? In setting out to answer this question, and to produce a method for diagnosing the direction of Roman surveying and planning from the landscape and structural remains, John Poulter's research eventually widened to ask the same question of Hadrian's Wall, its vallum and the Antonine Wall too. His analysis determines the probable directions in which the three structures were surveyed, and in so doing provides fascinating insight into their possible function - Hadrian's Wall, for example seem to have been set out with a view to maintaining a good view to the south, making signalling to the rear more of a priority in planning than observing to the north.