not real big on naval history, but.... isn't Nelson credited with revolutionizing naval warfare with his tactics in the battle of Trafalgar? Would no Nelson mean that battle is fought more traditionally? Britain would still win, perhaps even convincingly, but it wouldn't be the absolute trouncing as OTL, which means France/Spain still can present some potential threat to Britain's navy. Forget the land invasion. I've seen it argued that Napoleon threw away any potential military chess moves with his navy utterly destroyed, thus enabling Britain to truly rule the waves, such as blockade, etc, and this was a blunder that was amongst his biggest.