Police arrested Graham Smith and 51 others in central London as thousands of royal fans gathered in the capital for the event, saying their duty to prevent disruption outweighed the right to protest.

At 74, King Charles became the oldest sovereign yet to be crowned at London's Westminster Abbey, after a lifetime as heir to his late mother Queen Elizabeth II.

All the stops have been pulled out for the biggest display of British pomp and pageantry in decades, outstripping the queen's state funeral last September.

The cost of the coronation has been kept under wraps and the total sum is unlikely to be revealed until after event.

The congregation at London's Westminster Abbey will comprise Nobel Prize winners, religious representatives, and heads of state and foreign ministers, the palace says.

The introduction of the new oath is one of the changes to the centuries-old ceremony, which the palace wants to evolve, particularly to reflect the country's diversity.