That same year (1805) he brought home from Antigua despatches from Admiral Nelson, apprising the government of Admiral Villeneuve's homeward flight from the West Indies. On the way Bettesworth spotted the French fleet and alerted the Admiralty. His information led to Rear Admiral Robert Calder's interception of the Franco-Spanish fleet at the Battle of Finisterre. For his services, Lord Barham promoted Bettesworth to Post-Captain.