That famous signal was the perfectly logical thing to fly.
Sea Dog
. . .
"I am familiar with boats, Master."
Smoke rose from distant ships, rigging falling away from burning sails, explosions as black-red fires reached powder. Grey waves passed, clotted with smoking debris and worse.
Admiral Lord Nelson looked up. "We need to signal; something to hearten the men," he said to the tall man beside him. "Your advice has been incalculably valuable. What would you suggest?"
The man addressed the metal box by his feet. "What do you say, K-9? What's the most likely signal to rally these Englishmen?"
"England expects that every man will do his duty," the tin dog replied.
"Perfect." Nelson agreed.