Nobody learns Latin in school anymore, says Cleese. But God, this is a funny exchange and still resonates with anyone who ever studied with a maniacally strict grammarian.
I am sitting beside the shade of my favorite Brit and Number One Language Guy, fellow state-educated Catholic Anthony Burgess (a sourpuss in life, a bit of a giggle in death), and we’re both enjoying a hearty snort over this scene. But John Cleese is cutting it out of the musical!

Centurion: What’s this then? “Romanes eunt domus”? People called Romanes they go to the house?
Brian: It says, “Romans go home!”
Centurion: No it doesn’t. What’s Latin for Roman? Come on!
Brian: Romanus?
Centurion: Goes like?
Brian: Annus?
Centurion: Vocative plural of annus is—
Brian: Anni?
Centurion: Romani. (corrects graffito) “Eunt”? What is “eunt”?
Brian: Go!
Centurion: Conjugate the verb “to go”.
Brian: Uh…”ire”, uh…”eo”…”it”…”imus”…”itis”…”eunt”…
Centurion: So “eunt” is—?
Brian: Ah, uh, third person plural…uh, present indicative. Uh, “they go”.
Centurion: (pulling him up by his hair) But “Romans go home” is an order, so you must use the…?
Brian: (howls in pain) The imperative!
Centurion: Which is—?
Brian: Um—”I”! “I”!
Centurion: How many Romans?
Brian: Aaah! “I”! Plural. Plural. “Ite”. “Ite”.
Centurion: “Ite”. (correcting graffito) “Domus”? Nominative? (reads) “Go home”? This is motion towards. Isn’t it, boy? (pulls out sword and puts it to Brian’s throat)
Brian: (shrieking) Aaah, dative, sir! No, not dative! Not the dative, sir! No! Ah! Aaah, the…accusative! Accusative!! Aah!!! “Domum”, sir! “Ad domum”!
Centurion: Except that “domus” takes the…?
Brian: The locative, sir!
Centurion: Which is…?
Brian: “Domum”.
Centurion: “Domum”. (corrects graffito) “-um”. Understand?
Brian: Yes, sir.
Centurion: Now, write it out a hundred times.
Brian: Yes, sir. Thank you, sir. Hail Caesar, sir.
Centurion: Hail Caesar. If it’s not done by sunrise, I’ll cut your balls off.
I know you people like a little reward after such onerous reading, so here’s Miklós Rózsa’s “Parade of the Charioteers” from the 1959 MGM film, Ben-Hur.
And for good measure, here’s the fire of my loins John Wilson with his eponymous orchestra doing it on YouTube for the BBC Proms.