https://publications.parliament.uk/pa/cm201719/cmselect/cmfaff/780/780.pdf
https://www.nao.org.uk/wp-content/uploads/2017/07/The-Customs-Declaration-Service.pdf
https://www.instituteforgovernment.org.uk/sites/default/files/publications/IfG_views-eu-27-v5_WEB.pdf
https://www.crisisgroup.org/content/slivers-hope-middle-east