What is the theme of the poem "Anne Frank Huis" by Andrew Motion?

I think the dominant theme is liberty. The poem says that those looking at the pictures above Anne's bed find "not only patience missing its reward," but "one enduring wish for chances like my own: to leave as simply as I do..." and walk through Amsterdam. The kind of liberty Motion is talking about is as simple and basic as it gets, but it was a reward that was denied to Anne and her family despite their patience. The last stanza of the poem seems to speak to his recognition of the difference between his life and hers, and it obviously struck a nerve with him.