My reading of the last book of John Le Carré’s Karla trilogy, featuring George Smiley, Smiley’s People (1979), produced two more prescriptive comments. (There may have been more, but these caught my attention, possibly because both are in the HUGE database.)
The first is about the usage problem -ic/-ical, a topic dealt with by Robin Straaijer in an article from 2018. There are different preferences for either form between British and American English, as indeed seems to be the issue that is at play in the book:
“Yes, sir, ‘an extinct case of purely historic consern’, sir,” Strickland went on, into the telephone. […] “And Oliver Lacon proposes to have it included word for word in the D-Notice. Am I on target there, Oliver?”
“Historical,” Lacon corrected him irritably. “Not historic concern. That’s the last thing we want! Historical.” (p. 44)
From the context it appears that Strickland is talking on the telephone to Saul Enderby, the Circus’s new head after the uncovery of Bill Haydon as a double agent in the previous book, Tinker Taylor Soldier Spy (1974). “Not your style, I grant you,” Lacon continues, talking to Smiley, “why should he be? He’s and Atlantic man.” An Atlantic man showing preference for American grammar, it appears, may not have been Smiley’s style either.
The other instance is an example of a flat adverb:
“… Down here, please, sir, that’s the way! Walking normal still, please note,” the Superintendent had added, making a rare slip of grammar in his distraction. (p. 82)
Since the Superintendent is here addressing Smiley, we seem to have some interior monologue here. Adding up to that instance in Tinker Taylor Soldier Spy it looks as if we can add a strict view on linguistic correctness to the way Smiley is depicted. I have two more Smiley novels to go, The Secret Pilgrim (1990) and A Legacy of Spies (2017).