Possible Clues:

• Gavin --, English author of espionage thrillers
• He wrote spy stories, but his intentions were honourable
• He is in nearly all his own books
• Subtly allusive thriller writer will conceal his identity
• 'The Secret Servant', a novel by Gavin --, featuring character Harry Maxim for the first time
• Some terribly allergic thriller writer
• Some, or nearly all, of light novelist
• He appears in nearly all his own books
• A pose of Tom the mendicant (blame diet, perhaps?)