Wouldn't have been too much of a problem. Being thirsty by that time, they would head straight for Bradwell Marina and the Green Man, but they'd be in too much of a rush and forget to swot up their pilotage so would get stuck in the entrance channel. Then the locals could have thrown buckets of buckets of nuclear waste at them until they surrendered.......... Wouldn't fancy being in that pill box when an invasion fleet steamed into the Blackwater.