As the poem begins, the speaker seems to be midway through a conversation—perhaps with someone else, perhaps just with himself. In response to an unheard question, he says:
Yes. I remember Adlestrop—
He remembers, that is, a little town in Gloucestershire. Perhaps he's one of the few people not from Adlestrop who remembers Adlestrop; it's a hamlet so insignificant that the "express-train" doesn't even make a stop there.
One hot June afternoon, though, the train did stop in Adlestrop, "unwontedly" (or unusually), with the speaker aboard. What he saw that day will be the matter of this poem.
The speaker begins his story in a casual, everyday voice. The poem is written, roughly, in iambic tetrameter—that is, lines of four iambs, metrical feet with a da-DUM rhythm, as in "The name, | because | one af- | ternoon." Edward Thomas treats this meter more as a guideline than a rule, though; he throws in extra syllables or shifts stresses around wherever he pleases, making his speaker sound as natural as if he were telling a story in the pub.
Though the speaker's tone is easy and anecdotal, the poem's pace suggests his stop in Adlestrop meant something to him. As he looks back on that afternoon, he sounds unhurried, thoughtful, and calm, as if he's sinking into the memory. Listen again to the first line, and keep an ear on the caesura:
Yes. || I remember Adlestrop—
That full stop means the word "Yes" stands alone for a moment. Think how much chattier this line would feel if the speaker breezed right along with a comma: "Yes, I remember Adlestrop." Not only does the period slow the poem down, it asks the reader to stay with that "Yes," starting the poem on a note of reflective acceptance, or recognition, or embrace.
The speaker's careful phrasings help to set a mood, too. The speaker remembers his train pulling into Adlestrop, not on a hot afternoon, but on an "afternoon / Of heat." That wording suggests that heat was the main feature of this particular afternoon: this must have been one of those days when the weather seems to press down on the whole landscape.
Similarly subtly, the speaker doesn't simply "remember Adlestrop." He remembers "Adlestrop— / The name." His memory of Adlestrop, in other words, isn't of the town exactly, only of its name. That name, as readers will see, comes to represent not just a town, but a whole variety of experience.