#668 and #673: it depends who you're talking about. PoD was cognizant of the likely impacts of Brexit on operations some time (years) before the referendum and, like Eurotunnel, invested significant time and effort after it, starting the next day. This includes increasing French control infrastructure to combat increased processing times and, to be fair to PAF, they went along with increased staffing - hence the outcry when booths were left unstaffed:
https://www.doverport.co.uk/about/news/woefully-inadequate-french-border-resource-ruins-s/13687/.
PoD also recognised that more controls infrastructure would be required for the longer term... and this is what happened:
https://www.doverport.co.uk/about/news/port-of-dover-response-to-port-infrastructure-fund/13558/. Mind you, perhaps Ms Truss has a cunning plan for later this year.