In Chaucer's The Canterbury Tales, we're told that the Reeve always rides at the end of the procession of pilgrims going to Canterbury:
And evere he rood the hyndreste of oure route. (line 622; the text is available online).
Why is this?
The yellow bile or choler of this “sclendre colerik man” is at least partly expressed in suspicious wariness of others. In his position as Reeve (estate manager), this has served both “his lorde” and himself well, preventing them from being cheated:
Ther nas baillif, ne hierde, nor oother hyne,
That he ne knew his sleighte and his covyne;
They were adrad of hym as of the deeth. (603–05)
So he rides at the rear of the company because that is the best way to keep an eye on everyone else. There are some pretty shady and scurvy characters among the route of his nyne and twenty fellow-pilgrims, so to some extent this vigilance is warranted; but more importantly it is a characteristic of his temperament that he cannot well turn off even where it is inappropriate—wherein, precisely, lies the essence of humor of character, according to a theory most famously put into practice by Ben Jonson, and best articulated by Henri Bergson in his essay “Le Rire” (“Laughter”).