The King will host his first state visit as monarch as he welcomes the president of South Africa to the UK.
The Prince and Princess of Wales will play a key role in the visit, which includes a state banquet at Buckingham Palace.
William and Kate will greet President Cyril Ramaphosa and his wife, Tshepo Motsepe, on behalf of the King. They will then travel with the couple to the ceremonial welcome at Horse Guards Parade.
Two hundred horses and a thousand soldiers will take part in the military parade, with gun salutes fired from Green Park.
A state carriage procession will take the president, the King and Queen Consort and the Prince and Princess of Wales to Buckingham Palace for a private lunch.
The King will then show the president an exhibition of items from the Royal Collection relating to South Africa.
The state banquet in the evening will see the royal red carpet rolled out, with both the Queen Consort and the Princess of Wales expected to wear tiaras.
State visits are the ultimate diplomatic gift, and decisions on who gets invited are taken by the Foreign Office.
They provide the UK government with an opportunity to promote and boost international relationships.
This one though has particular significance for the King as it is the first of his reign.
He will make a speech at the start of the banquet, and his words will be carefully chosen, and the King could use this opportunity to discuss his vision for the Commonwealth.
It is also the first state visit to the UK since the pandemic, with the previous one in 2019 when the Queen hosted Donald Trump.
Throughout her reign, the Queen played host to 116 State Visits, and was known to take great personal interest in the small details.
Her last South African visit was over a decade ago in 2010, when she welcomed President Jacob Zuma.
President Ramaphosa is currently facing controversy at home, accused of covering up the alleged theft of $4m (£3.4m) in cash from his farm. The president denies any wrong-doing.
Do not expect any mention of that. This visit will be used to announce new projects between South Africa and the UK.
Prime Minister Rishi Sunak said: "South Africa is already the UK's biggest trading partner on the continent, and we have ambitious plans to turbocharge infrastructure investment and economic growth together.
"I look forward to welcoming President Ramaphosa to London this week to discuss how we can deepen the partnership between our two great nations and capitalise on shared opportunities, from trade and tourism and security and defence."