
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/695321/An_inspection_of_exit_checks.pdf

https://uk.reuters.com/article/uk-britain-eu-options/stairway-to-brexit-barnier-maps-out-uks-canadian-path-idUKKBN1ED23R

https://www.nao.org.uk/wp-content/uploads/2018/10/The-UK-border-preparedness-for-EU-exit.pdf