Who is Professor Alfred Vicary from The Unlikely Spy and what is their importance?

Alfred Vicary is the protagonist of this novel and is the man the author considers an "unlikely spy." An entrenched academic and professor of history at University College, Vicary is pulled into the war efforts by his longtime friend Winston Churchill. His thoroughness and attention to detail, combined with his World War I experience as a courier in the intelligence service for Britain, brings Vicary into MI5, and he is assigned the task of locating German spies.