Letter from France to UK (Lundy Island), Return to Sender and Taxed by UK Post Office

This is a registered letter posted from Le Havre in France to the British island of Lundy. Letter was return to France but a EUROPA 1 Puffin cinderella stamp was affixed by the Lundy post master (dully cancelled), mail had to return to France via mainland Britain and UK Post Master (in Bideford) decided to Tax the letter (due to the illegal cinderella stamp place on the envelope = hand written “Contrary to Regulation”) before forwarding it back to France.