It was certainly near the uplands round Cap Gris Nez (Promunturium Itium), but the exact site has been violently disputed ever since the Renaissance. Many critics have assumed that Caesar used the same port for his first expedition, but the name does not appear at all in that connection. This fact, coupled with other considerations, makes it probable that the two expeditions started from different places.
It is generally agreed that he first embarked at Boulogne. The same view was widely held about the second, but T. Rice Holmes in an article in the Classical Review (May 1909) gave strong reasons for preferring Wissant, 4 miles east of Gris Nez. The chief reason is that Caesar, having found he could not set sail from the small harbour of Boulogne with even eighty ships simultaneously, decided that he must take another point for the sailing of the more than 800 ships of the second expedition. Holmes argues that, allowing for change in the foreshore since Caesar's time, 800 specially built ships could have been hauled above the highest spring-tide level, and afterwards launched simultaneously at Wissant, which would therefore have been commodissimus or opposed to brevissimus traiectus.
Boulogne is presumed to have been the point of departure for the conquest of Britain of 43 under Aulus Plautius, although the only surviving account of the invasion, that of Cassius Dio, does not mention it. The emperor Claudius followed later with reinforcements, and Suetonius tells us he sailed from Gesoriacum.