In Blake's, "London," the speaker uses an adult narrator who is walking through the streets of London, a city that is not only the capitol of England, but the capitol of the British Empire. The city, as the speaker experiences it, falls short of what it should be, in the speaker's (and Blake's, by extension) perception.
Humans suffer under charters, regulations, popular opinions and mores, which all lead to "mind-forged manacles."
The speaker uses rhyme, with every other line rhyming in each stanza. He uses repetition: "In every..."; "charter'd"; "mark" and "Marks"; "cry." He uses alliteration: "And the hapless Soldiers sigh...."
The poem also uses allusion, referring to the "Chimney-sweepers" who appear in other poems in Blake's collections Songs of Innocence and Songs of Experience (in which "London" is included).
Rhyme, repetition, consistency of theme, and the linear walk through the streets of the narrator, create unity in the poem, with the speaker's opening of the final stanza leading to the final thoughts:
But most thro' midnight streets I hear....
And in the final stanza we see what sex and marriage in London lead to, what women having to sell themselves to survive leads to, and what marriage that must be maintained because society says so leads to.