Re: its not the Berlin wall FFS
"Isn't there a rule about Commonwealth citizens that Britain freely admits?"
Britain has been tearing that rule up for years. The barriers are now significantly higher than even a decade ago.
Commonwealth countries trading with Britain got well and truly shafted when it joined the common market. They'll be looking for payback if Britain has to go to them cap-in-hand for trade as it did in 1939-1949.