Party fit for a King! It's a late night for William and Kate as they depart Clarence House close to midnight after Charles's glittering 75th birthday bash... but was his biggest present his first phone chat with estranged son Harry in six months?

The Prince and Princess of Wales were seen enjoying a late night out as they departed Clarence House close to midnight after King Charles's glittering 75th birthday party.

But reports suggest the monarch's biggest gift this year was the call he received from his youngest son, Prince Harry, who allegedly phoned to wish his father a happy birthday - their first phone call in six months. 

Dressed to impress, Kate, 41, oozed elegance in an emerald Needle & Thread Alicia sequin-embellished recycled polyester gown, while Prince William, also 41, looked smart in a white shirt and jacket as he drove from the King's London residence.

They were joined at the King's birthday celebration by his niece Princess Beatrice, Princess Margaret's daughter Lady Sarah Chatto and the monarch's niece Zara Tindall and her husband Mike.

Looking effortlessly elegant, Zara, 42, stunned in Australian designer Rebecca Vallance's £640 Eva dress, featuring a figure-skimming silhouette and dazzling pearl embellishment. 

Sources close to Harry told the BBC he would be calling his father, who does not own a mobile phone, for his birthday. According to The Sun, Charles is understood to have also spoken with his daughter-in-law Meghan Markle during yesterday's call. 

Charles and Harry are understood to have had minimal contact for months, particularly since the release of Harry's tell-all memoir Spare, published in January, and a Netflix series, which was released the month prior to that. 

Buckingham Palace declined to comment, preferring to focus on His Majesty's Coronation Food Project. MailOnline has contacted Archewell for comment. 

Other guests at Charles' glittering birthday bash included the late Queen Elizabeth II's racing manager John Warren and Sarah Troughton, who is one of the Queen’s six companions (a role which replaced the former lady-in-waiting position) and oldest friends.

Sarah, the Lord-Lieutenant of Wiltshire, is a second cousin of King Charles via her maternal grandfather, who was a brother of the Queen Mother.

Penny Knatchbull also made a glamorous arrival in a stunning blue gown as she arrived at Clarence House. 

The Countess Mountbatten of Burma befriended Prince Philip at a polo match in 1975 when she was 20, became one of his closest confidantes despite being 32 years his junior and was pictured on walks with the Duke over the years 

Lady Susan Hussey, 84, the former lady-in-waiting to the late Queen Elizabeth II, was also in attendance, sporting an elegant blue shimmering gown.

Charles marked his 75th birthday with a gun salute and a sing-along at a food waste project followed by a reception for the NHS on Tuesday. 

Harry and Meghan previously said they had 'no contact' from Buckingham Palace about an invitation to Charles' 75th birthday event on the evening.

The Sunday Times reported that Prince Harry had turned down an invitation to the birthday bash, and will stay in California . But a spokesperson for the Sussexes told MailOnline that the couple had no idea about it.

A source close to the Sussexes told MailOnline that they were not invited to Charles party.

'They had not received any invitation and were unaware of any celebrations until the stories came out,' the insider said, adding: 'I'm sure the Duke will find a way to reach out privately to wish His Majesty a happy birthday like he has always done'.

A friend of the couple suggested the Palace could even have leaked the 'snubbing' story to take attention away from the recent royal visit to Kenya, where the King faced calls to apologise for Britain's colonial past.

'The story is being positioned in a way to make it look like the Duke is snubbing his father, which he is not,' the friend said. 'Considering the trip [to Kenya] didn't go well, this might be a welcome distraction.'

A 41-gun royal salute in Green Park, central London, a 62-gun salute at the Tower of London and a 21-gun salute in Edinburgh all marked Charles's milestone on Tuesday.

The King arrived in cheery spirits in Didcot, Oxfordshire, with Queen Camilla to launch the Coronation Food Project at a food waste distribution centre.

Among the many people he met there was Kelvin, who sells the Big Issue magazine, which is sold by homeless people to help them earn an income.

Photos show the King greeting Kelvin, who is holding a stack of the magazines. The special edition features a black and white portrait of King Charles on the front cover.

And dispelling the myth that royals never carry cash, photographs show Charles handing Kelvin a £10 note, to buy a copy.

The King, who enjoyed a working birthday before private celebrations, laughed as he was treated to a rousing rendition of Happy Birthday to mark his three quarters of a century.

Charles replied: 'Oh gracious!' after Baroness Louise Casey, who is helping to create his Coronation Food Project, asked whether he minded if guests serenaded him.

Baroness Casey told the monarch: 'I was wondering if it was all right…' at which point the King raised his eyebrows questioningly and looked around comically. He then quipped: 'Have you practiced?' to a group of volunteers behind him.

The King looked a tad bashful as everyone joined in, including Queen Camilla, who also clapped loudly at the end.

The monarch wore a warm-looking camel coat and a smart royal blue tie with a slate grey suit for the official visit, taking time to wave to those who'd gathered outside - many wearing disposable raincoats - to offer well wishes on his birthday. 

Queen Camilla, 76, opted for a stylish emerald green skirt suit with black knee-high boots and black leather gloves, and antique pearl drop earrings for the public outing - with both royals needing umbrellas to brave the inclement Oxfordshire weather.  

The Coronation Food Project was inspired and devised by the King, who has long been concerned about waste, particularly when it comes to food, and the cost of living crisis. More than 12million tons of food is wasted each year in the UK alone.

The project will work with, and crucially raise funds for, existing food waste projects around the country to save and circulate more surplus food and use it for social good.

It will help scale up nationwide projects and build warehouses, as well buy fridges, freezer and refrigerated lorries. The project is being led by Baroness Casey and Dame Martina Milburn and co-ordinated by the King Charles III Charitable Fund.

'We are beyond delighted about it. It is such an honour for us and support for the project just wouldn't have happened without you. We are incredibly grateful to you,' Baroness Casey told the King and Queen. 

Arriving in pouring rain, they met staff and volunteers in the warehouse, the King asking questions about how the surplus food is received and distributed to community organisations.

At one point, the monarch asked: 'I hope you have had a lunch break. There's plenty to eat!'

The King also took a peek inside a freezer and then outside viewed four Fareshare food vans loaded with goods for distribution. 'Are you just about to go out?' he asked one driver.

Although the engagement hadn't been publicised in advance, there was a small but vocal crowd outside who burst into another rendition of happy birthday.

Meanwhile 70 miles away in London, members of The King's Troop Royal Horse Artillery carried out the ceremonial tradition of a 41-gun salute for the King, lighting up a murky day in Green Park. 

The Honourable Artillery Company fired an additional 62-gun salute at Tower Wharf, Tower of London - an extra 21 for the City of London - at 1pm. 

North of the border in Edinburgh Castle, the Band of Royal Regiment of Scotland played their instruments, ahead of 16 Regiment Royal Artillery firing a 21-gun salute.

Back inside the Didcot hub's offices, Charles and Camilla popped into the kitchen where chef Alex MacKay was making a delicious array of hot food with a team of volunteers. 

'Happy birthday,' he told the sovereign. 'How did you know?' joked Charles.

The chef continued: 'Would you like to see what we are cooking, sir? This is all from surplus food.' The dishes included plates of fresh vegetables and a lentil and black bean chilli.

'I had hope to feed you but I understand we can't. Would you like to have a taste?' he added.

The King, who famously never stops for lunch, said he had another engagement to get to.

Before he left, Charles asked him: 'Are you from Australia?' 

Alex replied: 'Oh no, and we were getting on so well! I'm from New Zealand. You know what you do, sir. You ask someone if they are from New Zealand and for the Australians, that's a compliment!'

The King also spoke to food influencers including Bake Off's Crystelle Pereira, as well as the chief executives of several major supermarkets and food suppliers including Morrisons, Sainsbury's and Waitrose, alongside Amazon, ABF and Prince's, who have all signed up to the newly-created Food Alliance to help stop food waste and donate surplus produce.

There was also time to chat with Lord Bird, co-founder of The Big Issue, who launched the Coronation Food Project on Monday with a new portrait by Rankin of the King on the front cover.

He told the King: 'I haven't seen you for a quarter of a century.' 

'Has it been as long as that?' asked the King. 'You haven't changed a bit!'

Kelvin, who has sold the Big Issue off and on for 25 years during periodic bouts of homelessness, explained afterwards: 'It just shows he cares. He is reaching out to the general public. He is a good man.

'The Royal Family always try to help but he really does. The world is in turmoil and we need to all be together. We are all equal. He is using his position to facilitate change. His mother would be proud of him. She was a benevolent and kind person. '

Before Charles and Camilla left for another engagement, followed by a private dinner in London, the King unveiled a plaque to mark his visit before he and the Queen waved off four food distribution vans.

Later today, Charles will host a Buckingham Palace reception highlighting the work of nurses and midwives over the decades as part of the NHS 75 celebrations.

Among the guests will be around 400 nurses and midwives alongside the Chief Nursing Officer of England, Dame Ruth May, and Amanda Pritchard, chief executive of NHS England.

This morning, the Royal Family's social media accounts paid tribute to King Charles on his 75th birthday, posting a photobook-style montage of images showing the monarch from his very first public appearance as a baby to more recent times - and lots of key moments in between.

The 39-second clip was posted on X this morning by the @RoyalFamily account and rolls back the decades for the monarch as he celebrates a milestone birthday - showing some of the most important moments of his life and more intimate photos spent with family members through the years. 

The post shared two emojis, one of a crown and the other of a cake, alongside the words 'Wishing His Majesty The King a Happy 75th Birthday.' 

There are images of the late Queen, including one from 1948 when she was pictured for the first time in public with her firstborn. Charles is seen fast asleep wearing a royal christening gown in his mother's arms. 

Princes William and Harry also appear, although not together, with happy scenes from their childhood flashing past, including the moment the then Prince Charles and the late Princess Diana introduced their second son to the world at St Mary's Hospital in London in September 1984. 

There's also a November 1997 image of the then Prince Charles with a young Prince Harry as father and son are seen smiling together as they recorded their handprints in concrete while on an official visit to South Africa.

Elsewhere, a 1998 snap of Charles with Princes William on the slopes in the Swiss ski resort of Klosters, a long-time favourite of the royals, also appears.

The photobook-style montage opens with a blue-and-white front cover featuring a floral scene with bee imagery and the words 'Happy Birthday Your Majesty'. 

Stirring classical music provides the soundtrack as the montage races through the decades.