Plans are converging on that Saturday near the start of the summer although discussions over which other days will become official holidays are still going on, said a government official speaking on condition of anonymity before a public announcement.
Buckingham Palace declined to comment.
Almost 70 years to the day after his mother was crowned, the coronation will form the centrepiece of days of celebration to mark the beginning of the monarch’s reign.
King Charles acceded to the throne last month after the death of his mother, Queen Elizabeth II.
By June next year he will be 74, making him the oldest person to be crowned sovereign in British history.
It has been widely reported that the coronation will be a smaller, more modest version of previous ceremonies, with space for representatives of different faiths and community groups in line with modern Britain’s diversity.
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King Charles will be crowned alongside his wife, the Queen Consort, Camilla.
When Queen Elizabeth II was crowned in 1953 more than 8,000 guests from 129 nations travelled to Westminster Abbey in the centre of London, with temporary platforms erected to seat the guests, including every member of the British aristocracy.
Safety restrictions mean that nowadays the church can only hold about 2,000, providing a headache for planners.
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Last month, the UK Foreign Office spent days devising the seating plan for the queen’s funeral, mindful of diplomatic hierarchies and protocol.
The coronation ceremony itself is rich in tradition.
The king is seated on a throne known as Edward’s Chair, holding the sovereign’s sceptre and rod — to represent his constitutional control of the nation — and the sovereign’s orb — to represent the Christian world.
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After being anointed with oil, blessed and consecrated by senior clergy, King Charles will have the crown of St Edward placed on his head.
St Edward’s Crown — named after the last Anglo-Saxon king, Edward the Confessor — is made of solid gold and features over 400 gemstones, including rubies, garnets and sapphires.
The version which will be used next year, originally made for Charles II in 1661, is 30 centimetres tall and weighs 2.23 kilograms. It is usually kept under guard in the Tower of London.