https://www.nao.org.uk/wp-content/uploads/2018/01/Implementing-the-UKs-exit-from-the-European-Union-the-Deparment-for-International-Trade.pdf
https://www.socialeurope.eu/brexit-shows-us-real-first-world-problems-look-like
https://www.instituteforgovernment.org.uk/sites/default/files/publications/IfG_Brexit_customs_WEB.pdf