Interesting link 3refs. When the incident was covered in the Second World War documentary series they stated that the reason the Civil aviation flight carrying Howard was shot down was because either a Nazi Agent or sympathiser noted a well dressed man wearing a Homburg hat and smoking a cigar was seen about to board the aircraft. The JU 88 long range fighters which were based in France not in Spain were launched because they thought from the description that the man could have been Churchill. I think the bit about Franco and Luftwaffe aircraft being based in Spain refers to the period of the "Condor Legion" during the Spanish Civil War.