Father and younger son have not really been on speaking terms since Harry criticised his family in his memoir Spare in January.
But last night the monarch was expecting a transatlantic call that will lift hopes inside the royal household that one day they could all make up.
At Clarence House dozens of guests gathered for a birthday dinner.
They were mostly close friends but also a small number of other royals, expected to include the Prince and Princess of Wales and Princess Anne.
Charles was said to be in an exuberant mood after a busy day that included two official engagements: launching a food charity project and a reception for nurses and midwives at Buckingham Palace. “He loved it,” a senior royal aide said. “He’s had a very happy birthday.”
In London, the bells of Westminster Abbey rang in celebration. At noon the King’s Troop Royal Horse Artillery fired a 41-gun salute from Green Park. An hour later the Honourable Artillery Company fired a 62-gun salute near the Tower of London – an extra 21 for the City of London.
In London’s West End, the Piccadilly lights were emblazoned with a message to celebrate the King’s three-quarter century and the launch of his Coronation Food Project.
At 5.30 pm tourists and commuters in Piccadilly Circus saw Europe’s largest advertising display screen sharing the message: “Happy 75th birthday Your Majesty”.
It highlighted the Coronation Food Project, launched by the King and Queen Camilla earlier in the day at a surplus food distribution centre in Didcot, Oxfordshire.
It is designed to tackle the twin problem of the increasing numbers of people unable to afford to eat, while millions of tons of surplus produce is being thrown away.
The King was quoted on the giant Piccadilly screen, saying: “Food need is as real and urgent a problem as food waste – and if a way could be found to bridge the gap, then it would address two problems in one.
“To mark my 75th birthday in this Coronation year, it is my greatest hope that the Coronation Food Project will find practical ways to do just that.”
The birthday message was arranged by The Felix Project, London’s largest food rescue charity, which, along with FareShare, is supporting the project.
Charlotte Hill, of the former, said: “This unique birthday message has a deep and poignant purpose. The Felix Project recently found that one in four working families regularly struggled to afford enough food and one in 10 have less than £20 a week, after paying all their bills, to buy food.
“That is why the Coronation Food Project is vital. Without help like this we cannot ensure we have enough food, money and volunteer power to deliver much-needed, delicious surplus food to those that need it most.”
