https://blogs.lse.ac.uk/brexit/2019/08/12/boris-johnsons-real-agenda-the-singapore-scenario/
https://publications.parliament.uk/pa/ld201719/ldselect/ldconst/69/69.pdf
https://ec.europa.eu/commission/presscorner/api/files/attachment/867751/NA0620220ENN_002.pdf
https://ec.europa.eu/commission/sites/beta-political/files/customs_controls_0.pdf