Well, it certainly seems like "London" is more interested in the confinement side of things now doesn't it? Yes indeed. First and foremost, this is a poem about literal forms of confinement: chartering, a way of controlling, narrowing, and confining things that should be open (like rivers and streets). Then we've got that chimney sweeper, who for all intents and purposes is a slave worker; ditto that soldier (he's gotta do whatever the government tells him). On top of all this, there's those pesky "mind-forg'd manacles," the poem's metaphor for all the ways in which people dream up (that's the mind part) to enslave people. This could be governments planning wars, or governments mismanaging geographical space (the Thames, the streets), or even random people looking at things all wrong.
Free?! There is nothing free about London. Even children, the most "free" of all, are slaves—to the church (as chimney sweepers), to fear, or even to the corrupting curse of the harlots.
Not even the speaker is free in this poem. Just look at how the language of this poem is confined—the repetition of sounds and words mimics the poem's themes.
Death is all over "London"—literally. The title of the poem may well have been "London: the Dead City." Hearses, bloody palace walls, blights, and plagues—death is everywhere. In this poem's universe, all this death is the result of war-mongering governments ("palace") and corrupt institutions like the church ("blackning church"), which allow child labor, prostitution, and war. Things that formerly promoted life and unity, like marriage, now only create more death ("hearse"). Sadly, the picture is bleak—there seems to be no end in sight for all this death, a fact evident in the poem's extremely repetitive structure, word choice, and tone.
Youth is associated with death, rather than life, in this poem. This is totally backwards, which is the speaker's way of saying London is totally out of whack.
"London" is full of vampires. No, not the Dracula kind. Everybody is literally alive, but they're also really, really dead—inside.
Now hold on just a second. "London" is from Blake's Songs of Experience, not Songs of Innocence, right? Yep—which is why innocence is a major theme. Huh? Well, we don't mean innocence so much as the ways in which people have their innocence taken away (mostly infants and children). This poem is also interested in guilt, too. The church and the government, for example, should be innocent of wrongdoing but, strangely, are guilty of taking innocence away from children and infants. Sheesh.
Innocence? What innocence? In the London described in "London," there is no such thing as innocence anymore.
This poem cannot describe innocence because the speaker himself is not innocent. He's a dude that clearly has some experience of the world.