In fact the logical place to assemble 800 or so ships was in the large lagoon (where now there is farmland and a maze of drainage ditches) behind a coastal fringe of islands (where the modern ports of Calais and Dunkirk now sit) because in Caesar's day an estuary stretched all the way inland to the site of the modern town Saint-Omer. In 1944, French historian Albert Grenier, against the backdrop of Allied invasion of Normandy, reanalysed Caesar's text against modern understanding of wind, weather, tides, and siltation in the English Channel. He concluded Caesar's departure ports were likely to be Boulogne, Wissant, and Quentovic. All would later become important as Roman ports. The English side of the Channel also had many places that were Roman-era ports but were now far inland because of silting.