How a single breach can rewrite defensive assumptions

The comparison with airline-hijacking procedures before and after the September 11 attacks explains adaptation at the Dover Barrage. Before 2001, pilots often cooperated because hijackers were expected to seek leverage, a diversion, or negotiation rather than control of the aircraft as an end in itself. The attacks reversed that assumption and made keeping the cockpit inaccessible the safer rule. In the Channel, one submarine exposing a workable passage method could likewise turn an accepted premise into a vulnerability and trigger new countermeasures.