King Charles is celebrating his 75th birthday with a business-as-usual approach and the launch of a project to help people facing food poverty.
But it's understood that he will be getting a birthday greeting by transatlantic phone call from his youngest son, Prince Harry.
The King's birthday plans will also see him hosting a reception for NHS nurses and midwives.
Ceremonial gun salutes will mark the day, including at the Tower of London.
Public service rather than glitzy partying is being emphasised in the King's birthday engagements, although it is expected that there will be a private dinner for close family and friends.
Prince Harry, the Duke of Sussex, will not be there, but well-placed sources say that the US-based duke will be putting in a birthday phone call to his father.
The plans for a phone message might be seen as an olive branch, after claims that there had been no contact with Prince Harry about the birthday plans.
The centrepiece of the public side of the King's birthday will be the official launch of his Coronation Food Project.
This is intended to tackle the double problem of increasing numbers of people unable to afford food, while millions of tonnes of surplus food is being thrown away.
Highlighting the campaign in an article in the Big Issue magazine, the King said: "Food need is as real and urgent a problem as food waste."
The King told the magazine that "cost-of-living pressures" were resulting in "too many families and individuals missing out on nutritious meals".
The project aims to create distribution hubs to connect surplus food with what it says are 14 million people facing food insecurity.
An animation promoting the Coronation Food Project will be shown on Tuesday evening on the digital advertising hoardings at Piccadilly Circus in London.
There is a circularity to his launch of a food-sharing project on his birthday.
When the then-Prince Charles was born on 14 November 1948, there was still food rationing in post-war Britain.
To mark the birth of the then-Princess Elizabeth's first child, there was a scheme to provide a gift food parcel to every family who had had a child on the same day.
According to National Archives records, more than 2,600 gift parcels were distributed in this era of austerity, with items including soap, butter, dried egg, honey, marmalade, bacon and beef.
King Charles has been sharing the celebrations for his 75th birthday with other people of the same age, who were invited to a party at his house at Highgrove in Gloucestershire on Monday.
He is also marking the 75th anniversary of organisations of the same vintage, including the NHS, with 400 nurses and midwives invited to a reception at Buckingham Palace on Tuesday.
The King last week rebranded his charities as the King's Trust and King's Foundation, rather than Prince's Trust and Prince's Foundation, which will send another message of keeping working rather than slowing down or handing over the reins to the next generation.
He will be travelling to speak at the COP28 climate change summit in Dubai at the end of this month.
At the age of 75, King Charles is now the sixth longest-lived British monarch, behind Elizabeth II, Victoria, George III, Edward VIII and George II.
