Juan Pujol García, AKA Garbo was a British double agent without the British knowing he was. How is he perceived in historiography?

by Akasazh

His wiki page and his exploits alsmost are too incredible to be fiction. However I noticed that many cited works are popular history works, many of them based on accounts from Garbo himself and his handler in the British intel. I was wondering in what way his case is regarded by professional historians.

VivaTheBZH

What do you mean "without the British knowing he was"?