The poem takes place on 9/11. According to the poet, the speaker is an English trader stuck in the World Trade Center's North Tower after the first plane struck but before the tower's collapse. The poem was inspired by actual footage: Armitage has described the image of a bystander pointing a video camera up at a person trapped in the burning building and waving a white object.
The speaker addresses "You" throughout the poem. The identity of this "you" is never made clear within the poem itself, allowing that "you" to stand for any or all of the following: the person recording this footage, and, later, the viewers of that footage; the reader; the man's loved ones; the general public on 9/11; and humanity in a broader sense. Part of the poem's power is that the speaker doesn't really have a true destination for his words; no one can actually hear him, and he is going to die.
The reader knows this, creating dramatic irony and granting the whole poem a sense of inevitability and futility from beginning to end. These are the imagined thoughts of an anonymous, doomed man, spoken as if in real-time during the event and, in a way, after the fact. Here, he is both living and a ghost.
In the opening line, the speaker says, "You have picked me out." The speaker then describes his situation from the perspective of the camera/that "you." He forms part of a "distant shot of a building burning," that bold /b/ alliteration calling attention to the horror of the poem's setting.
The speaker then says "you have noticed now," that "now" implying that it takes a beat for whoever is looking at this "shot" to spot him. Really, they just spot the "white cotton shirt" that's "twirling, turning" in the distance; it's not clear yet whether or not actually see the speaker himself.
This stanza, like the rest of the poem, is chock-full of "-ing" verbs, or present participles. The building is "burning"; the white shirt "is twirling, turning." These words make the poem sound urgent and immediate. They wrench the poem uncomfortably into the present moment, forcing the reader to try to imagine what it was like to be in the speaker's shoes. The poem's immediacy rehumanizes the speaker, reminding the reader that he isn't just a symbol of the day's horror; ultimately, there is a real person behind the poem, even if these words are imagined. The asyndeton in this stanza and throughout the poem adds to the building sense of confusion and panic; there's no time for an "and" in "twirling, turning."
The poem uses quatrains (four-line stanzas), with every second and fourth line ending in an "-ing" verb and often with a full rhyme to boot (e.g., "burning"/"turning" in this stanza). This set-up makes the speaker seem at once frantic and frozen: he's also stuck on a particular sound just as he's stuck in a particular part of the building. He's moving, relentlessly waving that shirt, but firmly in place.