To be eligible for a United Kingdom passport, one must be a British national. This can either be by birth or naturalisation. Citizens of British overseas territories are also eligible for a passport. Additionally, British subjects, British protected persons and British nationals abroad can get a UK passport.
Are You a British Citizen?
As mentioned in the overview, British nationals (in the UK or overseas), British overseas territories citizens, British subjects and British protected persons are the only people eligible to receive a British passport. One is considered a British citizen if he was born in Great Britain or, if not born in the UK, is eligible for naturalisation by meeting various requirements.
If a child is born on or after Jan. 1, 1983, outside the UK but has a UK-born mother, she is eligible to register for British citizenship. Children born outside the UK but adopted by British parents are also eligible for citizenship. A child born before July 1, 2006, whose father is British but not married to their mother, can also qualify for citizenship. Additionally, children whose parents gave up and then resumed British citizenship qualify and children born abroad to British parents but who are now living in the UK are also eligible. For further rules and requirements, see the Home Office's page on citizenship in the References section.
Citizenship through Marriage, Partnership or Residency
Unless a woman married her British husband before Jan. 1, 1949, she is not eligible for citizenship automatically. The same rule applies to those in a civil partnership. However, persons who are over 18 and have been living in the United Kingdom for the last five years (three years if married to or partners with a British citizen) can apply for naturalisation as a British citizen.
Citizens of British Overseas Territories
People born in British overseas territories who are citizens of the territory are eligible for a passport. If a child was born outside these territories but his parents are British overseas territories citizens by descent and have lived in that territory for three consecutive years without leaving the territory for more than 270 days, he is eligible for British overseas territories citizenship.
Serving the Crown
Persons who do not meet the five-year residency requirement may be eligible to register as a British citizen if they have been or are serving the crown under the government of a British overseas territory or have been or are holding a responsible post, given outstanding service and have a close connection with the United Kingdom.
British Nationality (Hong Kong) Act 1997
Under the British Nationality (Hong Kong) Act 1997, a person can register for British citizenship if he is an ordinarily resident of Hong Kong at the time of application and had been an ordinarily resident in Hong Kong on Feb. 3, 1997. If the child was born on or after Feb. 4, 1997, he must have been an ordinarily resident at the time of his birth. An ordinarily resident is someone who lives in Hong Kong full time, does not breach immigration rules and moved to that area voluntarily.
People who gave up their British citizenship can also apply for a passport as long as they resume their British citizenship. Persons interested in resuming citizenship may contact the Home Secretary for advice before making an application.