Special Branch at Croydon monitored all international flights. They may have known that this was no joy ride. Major Pollard was an experienced MI6 officer, Spanish-speaking and with firearms expertise. He had worked under journalistic cover in Ireland, Mexico and Morocco. His superiors in the intelligence services probably had a fair idea of his object in flying to the Canary Islands. The commander of the Spanish garrison there was one General Francisco Franco, whom the Spanish Republic had sent there some months before to keep him out of the way. Franco already had a reputation for his part in suppressing the Asturian miners, and his hostility to the Republic. Had a Spanish plane landed in the Canaries the authorities might have been alerted, but the British flight didn't arouse suspicion.
The plane flew Franco and right-wing conspirator Emilio Mola to Tetuan in Spanish Morocco. On July 18, 1936, some Spanish generals announced a coup against the elected Socialist government. Franco arrived in Morocco the following day to raise support from Spain's African army.
http://randompottins.blogspot.co.uk/2006/09/british-friends-of-franco.html