A mechanized army is useless without fuel, and in 1942 the Allies faced a logistical nightmare: coastal tankers crossing the English Channel were slow, weather-bound and easy targets for the Luftwaffe. This episode tells the story of Operation Pluto, Pipeline Under the Ocean, starting with Lord Mountbatten's question about laying a pipeline across the Channel and the experts who declared it impossible. We follow engineer Clifford Hartley's lateral leap of pumping oil through the hollow core of an undersea telegraph cable, the layered lead, steel and jute construction of the HAIS cable, and how 1,500 psi pressure allowed aviation spirit and diesel to flow through the same pipe without mixing.

When Britain ran short of lead, Bernard Ellis proposed a mild steel alternative, the Hamel pipe, which required the Conundrum, a 60-foot floating steel ...