After the fall of France, as Britain prepared for an expected German invasion, a Royal Navy officer in the Directorate of Miscellaneous Weapons Development calculated that Hitler could use slave labour to build two Channel tunnels in 18 months.
法国沦陷之后，作为英国应对预期的德国侵略的准备，一位英国皇家海军综合武器发展部（英语：Directorate of Miscellaneous Weapons Development）的军官计算出，希特勒可在18个月内使用奴隶建造2条隧道。