Napoleon knew that the French fleet could not defeat the Royal Navy in a head-to-head battle, so he planned to lure it away from the English Channel through diversionary tactics. The main strategic idea involved the French Navy escaping from the British blockades of Toulon and Brest and threatening to attack the West Indies. In the face of this attack, it was hoped, the British would weaken their defense of the Western Approaches by sending ships to the Caribbean, allowing a combined Franco-Spanish fleet to take control of the channel long enough for French armies to cross and invade. However, the plan unraveled after the British victory at the Battle of Cape Finisterre in July 1805. French Admiral Villeneuve then retreated to Cádiz instead of linking up with French naval forces at Brest for an attack on the English Channel.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"):  Napoleon's naval plan came apart after British triumph at which Battle?
the Battle of Cape Finisterre