Last Updated September 5, 2023.
The main character in Larkin's "High Windows" is the speaker. Aside from the speaker, there are some minor characters, namely "a couple of kids" and a priest.
The speaker seems nostalgic for his youth and looks enviously upon those who are young while he is old. He characterizes youth as the time when "Bonds and gestures [are] pushed to one side" and when everyone goes "down the long slide / To happiness, endlessly." The speaker then suggests, however, that his own childhood was not quite as free and joyful as this. Describing himself "forty years back," he describes a boy who was, unlike the previous generation, free from the burden of "sweating in the dark / About hell and that." In other words, he was granted more religious freedom in his youth than those who had come before, who perhaps were jealous of him just as he is now jealous of the sexual freedoms enjoyed by the younger generation.
At the end of the poem, the speaker describes "high windows" beyond which there is only "deep blue air, that shows / Nothing, and is nowhere, and is endless." It is debatable as to whether this is a description of youth in general or whether it is a description of life from his present middle-aged perspective. If we interpret it as a description of youth, we might infer that he looks enviously upon the transcendental freedom of youth. This would imply, in turn, that he doesn't feel like he has this freedom in his middle age. We might also interpret the description of the "endless" blue sky beyond the "high windows" as a description of life once youth has passed. In this case, an interpretation in keeping with the rest of the poem might be that the speaker thinks of his middle-aged life as interminably meaningless now that he has lost his youth.
The "couple of kids" mentioned in the first stanza personify the liberty, and specifically the sexual liberty, of young people today at the time the poem was published (1974). The fact that they can take "pills" or wear a "diaphragm" implies that they can enjoy casual sex without thinking too much about the consequences—or at least without thinking as much as the speaker might have had to think when he was their age around the 1930s.
The priest referenced in stanza four is grouped together with "his lot" and also "God." The phrase "his lot" is dismissive, even scornful. The speaker notes that in his youth he was more free than the generation of believers who had come before, who may have envied his ability to say what he really thought about the priest and not to spend his nights worrying about hell and sin. He compares this religious freedom to the sexual freedom enjoyed by the "couple of kids" he now observes as a middle-aged man.