Châteaurenault was shaped to resemble an ocean liner more convincingly than Guichen, supporting deception during an approach to merchant traffic. The disguise could work briefly in peacetime or at long range, but major liners were rare, followed recognizable routes, and were valuable enough for warships to investigate. Wartime liners also served as troopships, fast transports, and armed merchant cruisers, making their identification militarily important in its own right. A Type 23 frigate presenting a fishing-vessel radar return has the same weakness: camouflage cannot make an implausibly placed contact uninteresting.
Chapter · 15:23-20:16
Why Châteaurenault's liner disguise had limits
A liner-like bow, hull form, and four funnels could delay recognition at long range, yet unusual liner movements would still attract wartime inspection.