Dover Castle is the gateway to England. Dover was one of the harbours of the Saxon Shore and the base for the Roman fleet, Classis Britannica. Its Roman lighthouse probably dates from the 1st cent. ad. There was certainly some Saxon fortification there but the present castle was started in the reign of Henry II and ready for use in 1185. Its most remarkable feature is that the large keep is itself protected by further curtain walls. It was one of the last rectangular keeps to be built before castle design moved on to polygonal or circular towers. The keep is similar to that at Newcastle Upon Tyne, finished a few years earlier, and by the same master builder, Maurice the Engineer. In 1216 it was held by Hubert de Burgh for King John against several weeks' siege by Louis, dauphin of France. Its subsequent history was surprisingly peaceful and the heavy fortifications added during the Revolutionary and Napoleonic wars were never called upon. The lord warden of the Cinque ports is also constable of Dover castle.