A book-length poem about nuclear tensions of the cold war period has won the Costa poetry prize. Assurances by JO Morgan uses a mix of versed and unversed passages to eavesdrop on the thoughts of those trying to understand and justify their roles in keeping peace by threatening war. The Costa judges said they were “ gripped by this polyphonic book-length poem and dazzled by its originality and inventiveness”.

JO Morgan, the son of a former RAF officer who was involved in maintaining Britain’s airborne nuclear deterrent, was born in Edinburgh, and now lives on a farm in the Scottish Borders. He is the author of five previous collections, each a single, book-length poem. Natural Mechanical won the Aldeburgh first collection prize, and was shortlisted for the Forward prize for best first collection; Interference Pattern was shortlisted for the TS Eliot Prize.