Trafalgar's two columns and its flag officers

How were the ships split into groups and squadrons at the Battle of Trafalgar?

Nelson and Collingwood led the two British columns, while the wider fleets included more senior flag officers than the famous names alone suggest.

Nelson and Collingwood each led a British column of ships of the line into the battle. The wider command structure also included additional British, French, and Spanish admirals and commodores. Tactical formation and senior command are separate questions. The hesitant attempt to count every flag officer shows why a precise order of battle requires more than recalling Nelson, Collingwood, and Villeneuve.