This is complete nonsense! Inward immigration has gone UP since Brexit, the cabinet is more brown/black than ever before, and the establishment clearly intend to do nothing whatsoever about the porous border in the south (don't be fooled by the laughable Rwanda holding camps initiative, the main motive of which is likely to funnel even more to the legal system etc.).
OTOH I would agree that the government (regime?) are delusional, but I would extend this to the entirety of the establishment, who seem to have departed from reality a long time ago, and seem to believe that the correct response to the UK's reduced circumstances and the population's temerity in daring to vote against globalism is to hasten its destruction.