I wouldn't say it does NOT work. that almost sounds like trying to state a fact, when it isnt.
I found the bit to be hilarious

It's bleeping funny.
"'Extremely High Voltage.' Well, I don't need safety gloves, because I'm Homer Sim" - Frank Grimes

It is funny.

i think it's funny.

I liked the sudden non-finish to the movie; it had the feel of a classic Flying Circus sketch. I'm with the OP on the guard scene, too. There's nothing about it that exhibits the Pythons' cleverness with wordplay.
"You may have come on no bicycle, but that does not say that you know everything."

by UneOmeletteFromage
It's a dud within an otherwise really funny movie.
The only scene i don't like is how they finished the movie (ie, they didn't). your example is definitely 'over-cooked', but still amusing if not outright funny.
Its ridiculous to critique a movie with the argument 'it's not real, so it doesn't matter'

The hiccuping is the only part that doesn't work.
I'm straight up lovable, son.

It absolutely DOES work.
"Everyone is ignorant, only on different subjects". Will Rogers (1879-1935)

For me the scene is perfect.
The Pythons were always great at taking their skit to the limit, and then to 11.
Don't lend your hand to raise no flag atop no ship of fools.

worked me though really funny not dragged at all.

It's not my favorite scene in the movie, but it works for me. My favorite bit is when the prince "sneakily" writes the note and shoots it out the window, they keep cutting back and forth between him and the two guards obliviously smiling at him Keep a close eye on Graham Chapman's face. I promise you, you will laugh.

Yep, it's consciously overcooked for such a pointless moment, while the delivery of the actors keeps it funny.

the Pythons do these kinda scenes to torture the audience. it's intentional.

It's a dud within an otherwise really funny movie. - Stacked_All_Cattywompus
Recently I saw
Spamalot
, the stage musical based on
Holy Grail
and other parts of the Python catalog. (This was a local repertory company version and not a big-name version.) The "make sure 'ee dusn't leave" scene is in the musical, and it was the flattest scene in what was a very lively and well-received performance. So, it doesn't work on film and it doesn't work on stage, either.
I mean, the joke lasts like five minutes, even though it ceased to be funny after about 15 seconds. They just overcook it to death!
Unfortunately, that seemed to inspire Mike Myers, who loves to drive a joke into the ground in every film of his I've seen.
"We hear very little, and we understand even less." - Refugee in Casablanca

"One rabbit stew coming right up!"
"I will not go down in history as the greatest mass-murderer since Adolf Hitler!" - Merkin Muffley

This message has been deleted.

Yeah, I agree. In a movie where almost every scene is full-on laughs that one is where they really dragged it for too long. But IMO it's not as bad as the ex-leper in Life of Brian. Now THAT was a stretched joke if there ever was one.

I like to think they made up for that part with Herbert shooting the arrow with the note on it out the window with the moron guards just smiling at him.

"Make sure the prince doesn't leave the room."
I've always hated that scene. It's a dud within an otherwise really funny movie. I mean, the joke lasts like five minutes, even though it ceased to be funny after about 15 seconds. They just overcook it to death!
Terry Gilliam is sometimes prone to overcooking scenes. They just go on and on till you get annoyed. I guess he just goes overboard sometimes, maybe on purpose, who knows?
I wonder which of the Terry's directed the Lancelot killing spree at the wedding reception? That was wildly funny.
"I've seen things you people wouldn't believe" - Roy Batty, Blade Runner

Utterly disagree OP. Yes, they drag out the joke on purpose, but the delivery of Palin and Idle is what makes it funny.
'then, you must cut down the mightiest tree in the forrest, wiiiiiiiiiiiiitha HERRING!'

It's painful and seems to last an eternity. Makes you want to punch them.
The Swamp Castle scene is saved by Lancelot running amok through the castle which is one of the highlights of the film.

It was funny. And it only lasted two minutes.
Rebuild the WTC exactly as before and keep old movies accurate!

I love that scene! It's my second favourite of the movie (after the bridge guy), but I agree about the hiccupping guard he didn't add anything to that scene.

You're crazy. That's the funniest scene in the movie. And the rabbit and bridgekeeper come in a close second and third.
I did sixty in five minutes once