Do citizens from Commonwealth realms like Australia, Bermuda, Canada?
Yes they do ever since the Commonwealth Immigration Act was passed in 1962 which restricted the rights of citizens of the Empire and Commonwealth to reside and work in the UK. Prior to that Australians at least were issued with a British Passport if they need to travel. Note that contrary to other answers, British people have never required a passport to enter the UK. That this is still the case was confirmed to me by an immigration officer at Heathrow when I last visited the UK in January. As the Immigration Act states: A person claiming to be a British citizen must prove that he has the right of abode in the United Kingdom by producing either: (i) a United Kingdom passport describing him as a British citizen or as a citizen of the United Kingdom and Colonies having the right of abode in the United Kingdom; or(ii) a certificate of entitlement duly issued by or on behalf of the Government of the United Kingdom certifying that he has the right of abode.