https://www.nao.org.uk/wp-content/uploads/2018/10/The-UK-border-preparedness-for-EU-exit.pdf
https://www.instituteforgovernment.org.uk/sites/default/files/publications/IfG_views-eu-27-v5_WEB.pdf
https://institute.global/news/the-inbetweener-brexit
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/502291/54284_EU_Series_No1_Web_Accessible.pdf