Rhythm in William Blake's London?

Since the rest of the poem is iambic, it wouldn't make sense to say this is trochaic. However, it's definitely clear why one would think, just seeing this stanza, that it's trochaic. Given the theme of the poem and the tone of this stanza in particular, the fact that the meter here seems to invert itself is pretty significant in terms of expressing the turmoil of the politics in England at the time of the French Revolution.