‘Trains show us that freedom and constraint are a matter of dosage,’ Patrick McGuinness wrote recently in the LRB. He quoted Klaus Kinski’s character in the 1966 film of Dr Zhivago, ‘shaking his chains, an anarchist headed for the camps’: ‘I am the only free man on this train. The rest of you are cattle!’ ‘Soul’, a poem Pasternak wrote in 1956, is one of 20 on display in another meditation on poésie des departs, in Bloomsbury Square until tomorrow.