From what little I have read about Cabrera, the British knew about the island.

At least one British Naval Officer’s memoirs mentions sailing by the island and sending supplies there although apparently not authorized.

Also soldiers from other nations, prisoners on the island, were recruited by the Allies, leaving pretty much only French prisoners remaining there.

“Baron Halberg, an Austrian officer in the service, was sent by me to Cabrera to choose out the Germans….” Lieutenant General Whittingham was allowed to recruit up to 600 Germans held on Cabrera in 1811.

Also, some 150 prisoners, including many from Cabrera, were sent to Scotland in March 1811. Apparently officers on parole.

Good hunting.

Ron