Read what it says on the British passport, the Northern Ireland bit is a giveaway please log in to view this image
Ok lets try it this way then; How does 'Theresa' solve the fact that if she imposes a border between Ireland and Norther Ireland then she can not gain a deal with the EU as Ireland will veto (not to mention the fact that she risks breaking the union or destroying the last 15+ years of peace) But if she moves that border between Northern Ireland and the mainland of UK then she loses her majority as she's propped up but the DUP. How do you think 'Theresa' sorts that?
Which is why you apply for a UK rather than a British passport https://www.gov.uk/apply-renew-passport because https://www.ordnancesurvey.co.uk/bl...ference-between-uk-britain-and-british-isles/
please log in to view this image Afraid I don't have one just the standard United Kingdom of Great Britain and Northern Ireland passport.