An applicant is not entitled to a Canadian passport just because he happens to hold a British passport. It took me and the old woman 10 years before we eventually got Canadian citizenship.
We have four passports, I guess that makes us quadruple passport holders.
PS, Northern Ireland is part of the UK, like Scotland and wales, that's why people who are born there are entitled to British passports. Canada is a separate country with its own government and currency etc etc. A Canadian is not entitled to a dual British passport, even if he is married to a Muslim.