Is This Stuff What British People Eat???

Yesterday was a free day. The birds were singing, there were “Ferris Bueller clouds” in the bright blue sky, and a gentle breeze, and so of course I got sick the day before and had to stay at home. But this turned out to be a productive day nonetheless. My place was really messy, so I spent most of the day sorting, organizing, and tossing stuff in the garbage. As I was going through, discarding things in the kitchen that had grown a layer of grey mold (everything- I am not even exagerating) I found this jar of Marmite. Contains various vitamins, 100 percent vegetarian, yeast extract… this looks like something that my father would recommend to treat you for whatever might be ailing you at the moment.
So I unscrewed the grimy yellow cap, and was treated to a whiff of stuff that smelled like a mix of Kyolic (fermented garlic infusion of nastiness), vinegar, and Karo syrup. It was thicker than honey, and had the color of spoiled chocolate pudding. Surprisingly (maybe not really), no mold had grown on this. Even if it had, this stuff could not be any nastier that it was in its natural state.
I know Brits eat some strange stuff. Steve’s Toad in the Hole and other lard filled dishes are proof of this. I mean, are you supposed to find pubes in this dish traditionally, or was that just a special treat created in honor of Pete? Anyways, what did Harvey (my predecessor) use this stuff for? Since it was in the kitchen, I can only assume he ate or drank it in some form. I was thinking, are you obligated to eat disgusting things if you are a vegetarian? I think if I were vegetarian, I would opt not to eat Marmite, even if it made me a pseudo-vegetarian, and all the other vegetarians looked down on me (while enjoying a heaping tablespoon full of stinky goodness). I find the other argument, that it contains vitamins, not sufficient to get me to put this stuff in my mouth. I prefer my vitamin fortified Froot Loops and Kix thank you very much!
Has anyone eaten this stuff? If so I am curious to know:
1. Why?
2. How?
3. Would you ever do it again?
4. Is this stuff big in the U.K.?
5. Is it traditionally served with pubes?