It's a valid point, and I wouldn't have done it except a desire to compare executions. Like I said, this technique is VERY common to sketch comedy. Key and Peele, a VERY talented duo, do this in the majority of their sketches, and like the Monty Python sketch above, the premise is blatantly obvious and THEN escalates. What I love about this sketch is how you don't see it coming. You were warned of it, and it would be interesting to have seen how quickly you caught it had you not.
Figured out where it was going at 1:40
(got Andy's permission for this)
I would say that 1:45-1:55 would be where the viewer really catches on without having a clue in advance. That's over halfway through the video, and by that point Mitchell is building into a signature rant. Of course, once you know, there are clues prior to that. From 1:18-1:34 there are several clues in Webb's expressions that hint that he was agreeing more out of politeness than an accurate appraisal. That's really subtle. However, there is a risk here. Best case scenario, you are going almost a minute and a half with no comedy. That's a long time for a sketch to have no payoff.
So why does this work so well?
The obvious answer is faith. I love these guys, and am willing to wait for the joke because I'd already seen so many cleverly done sketches from them that I was willing to give them benefit of the doubt. However, I've shown this clip to many unfamiliar with Mitchell and Webb, and it consistently goes over well, showing that such faith isn't needed. So let's look at what else keeps the audience watching. Warning, this review is MUCH longer than the video.
First off, look at the image at 0:00, the opening shot. You see a man clearly troubled, reason unknown. Footsteps, echoing throughout the chamber, approach, and the man turns, sees who it is, and pulls back, clearly uncomfortable. He mainly keeps his gaze away from the man, only looking at him twice (at 00:16 and 00:18), both times peripherally and with a hint of fear. Without so much as a greeting or request to join, he sits down right next to him.
At this point, we have no clue what is going on, but we are supposed to feel sympathetic for the first man (Webb) and some sense of foreboding for the second man (Mitchell). His presence isn't wanted, and given the emotional distress exhibited by Webb, one might even think that Mitchell is in some way to blame. There's a story, a rich one, being hinted at, a serious emotional conflict, and the viewer wants to know what it is.
The tone suddenly changes as Mitchell offers a soft, friendly greeting and Webb asks if *he* is imposing, with Mitchell insisting he is not. Suddenly, the story becomes one of a troubled young man and a wise, caring samaritan. A full 20 seconds is spent just establishing Mitchell as kind, empathetic, and genuinely interested in helping before whatever is troubling Webb is revealed. You see the concern on his face, and it is very convincing. Much like Webb, the viewer is charmed by this character, made more comfortable in his presence. If you are actively looking for comedy at this point, you are probably expecting it to come from Webb, seeing the kind, patient vicar's kindness tested by some ridiculous confession. Personally, though, I'm still looking for the story, wanting to know why Webb is so troubled.
We soon find out. Webb, it seems, has feelings for a girl-Mitchell stops him from giving her name, once again demonstrating his wisdom. He then speaks Webb's name, showing that this is someone he knows. The video, at this point, has given us 40 seconds now portraying this character as I'v described, really reinforcing it. None of it, however, seems forced. This character is believable. In addition, Webb is confessing a problem that all of us can sympathize with, and we want to hear what the wise, kind man has to say about it. We want to hear it so badly that we miss the first hint that Mitchell *might* not be as insightful as we think.
At 1:06, Mitchell makes his first assumption, with Webb confirming it. Was he right, though? Look at Webb's eyes at 1:09. Is he looking away because he's ashamed, or because Mitchell was wrong but he, like us, so wanted the guidance that he was willing to overlook it? Watch his eyes, inflection, and general body language from there until 1:18. Is this a man relieved to have a great weight off of his chest or someone just reluctantly agreeing because he wants to keep the conversation going? Notice how he immediately follows with the word "but," another clue that Mitchell might be a bit off the mark. Mitchell cuts in, though, with another assumption, a rather aggressive one, and at 1:26 we again see Webb look away briefly. At 1:33, we get our last clue, as Webb vocalizes his difficulty confirming Mitchell's latest assumption (the third one thus far). Did he do it because he is uncomfortable admitting how much it bothers him? Given that he was sitting alone when the clip began, it is easy to perceive him as the strong, silent type. Of course, by this point, many are starting to come around to the possibility that Mitchell is wrong.
1:45-1:55 is the confirmation. If you suspected the game prior to that, then your suspicions are confirmed. If you hadn't, then you likely view this scene as something of a turning point. This is actually the boat I was in. Despite all the clues I referenced earlier, I rationalized them all away. From here, there isn't as much to talk about (much to your relief, I'm sure). Mitchell's claims become bolder, and Webb becomes more detached. At 2:17 Webb corrects him with mild assertiveness, for the first time conveying that he isn't interested in hearing more, but the camera rapidly pans to Mitchell, and he is lit more brightly, illustrating that it is truly about him now, and Webb is just his unfortunate audience. Like Webb, we have a morbid curiosity for hearing the rest, and Mitchell doesn't disappoint. It is dark and disturbing and beautifully paced.
Finally, at the end, there is one last gift, with Mitchell offering some parting advice, his tone and eyes having reverted back to those we were introduced to just three minutes ago.
Sorry to be so wordy, but I wanted to show how much is being done in this video. This is how a visual medium is supposed to be used, conveying emotions and even information without having to come out and say it.