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King Charles's coat of arms will feature on the front of all new passports from December, the Home Office has said.
Natural landscapes from all four UK nations will also feature inside the updated documents, including Ben Nevis, the Lake District, Three Cliffs Bay and the Giant's Causeway.
It is the first full redesign of British passports in five years, when they changed from burgundy to dark blue following the UK's departure from the European Union.
Passports featuring Queen Elizabeth II's coat of arms would remain valid until their expiry date, the government said.
Passports have been issued in the King's name since 2023, with their pages referring to "His Majesty", but the late Queen's coat of arms has remained on the cover.
The King's coat of arms features the rounded Tudor crown he chose as his royal cypher upon taking the throne in 2022.
As part of the transition from one reign to another, images and insignia of the King have gradually been introduced - including on stamps, coins and banknotes - with an effort to use up existing stocks rather than have an abrupt change.
By convention, the King himself does not have a passport because it is a document issued in his own name.
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All new passports will feature the above coat of arms from December
The new passports will also feature updated security features, the Home Office said, including the latest anti-forgery technology - making them "harder to forge or tamper with".
Migration and citizenship minister Mike Tapp said the redesign marked "a new era in the history of the British passport".
"It also demonstrates our commitment to outstanding public service - celebrating British heritage while ensuring our passports remain among the most secure and trusted in the world for years to come."
The government advised people to check the validity of their passport and, if needed, apply to renew them in good time ahead of travelling.
UK passports in their modern form, with a photo and signature, have been issued since 1915. The first security watermark was added in 1972 and machine-readable passports were introduced in 1988.