Penguin's gain was poetry imprint Cape's loss. Cape was first approached to publish the book, but rather counter-intuitively turned it down. Pity. Book of Longing is now one of Canada's best-selling poetry books of all time.
And Cohen, after all, was one of Jonathan Cape's poets, in 1969. But the tendency in London poetry publishing, to not publish good, popular Canadian and American poets, is a strong one. I'd go so far as to argue that such an insular editorial approach actually weakens general interest in and respect for contemporary poetry in the UK, by falsely regulating the sense of how exciting, dynamic, and even popular North American poetry - indeed, potentially, all poetry - is - or can be.