King Charles reveals 'wonderful messages and cards' after his cancer diagnosis have 'reduced me to tears' as he holds first face-to-face meeting with Prime Minister Rishi Sunak at Buckingham Palace since revealing he is battling the disease

King Charles III appeared in good spirits as he was seen publicly undertaking royal duties for the first time since it was announced that he has been diagnosed with cancer.

His Majesty, 75, beamed as he met with Prime Minister Rishi Sunak at Buckingham Palace today, having previously carried out audiences with him remotely from Sandringham.

The monarch told Mr Sunak that he has received 'so many wonderful messages and cards' since his shock diagnosis that he has been 'reduced me to tears most of the time'.

The prime minister reportedly told the King that it was 'very nice to see you', to which Charles responded: 'A bit of a gap... I'm afraid.'

Mr Sunak also said it was 'wonderful to see you looking so well,' to which the King jokingly replied: 'Well, it's all done by mirrors, really.'

Before the pair's private discussion, the King also met with members of the Privy Council in person on Tuesday evening.

Charles' profound sense of duty and strong work-ethic has seen him continue working privately through treatment, but this is the first time the King has been pictured carrying out royal duties.

The monarch is pausing public engagements as he undergoes treatment for an unspecified form of cancer.

It was discovered by doctors while Charles was treated for an enlarged prostate in late January.

His diagnosis was announced by Buckingham Palace just days later as it was confirmed doctors had noticed a 'separate issue of concern'.

Prime Minister Rishi Sunak reassured the nation when he previously said that King Charles' disease had been 'caught early'. 

The monarch is now spending much of his time at his Norfolk retreat Sandringham, although sources say he is well enough to continue a small number of face-to-face meetings. He will also be carrying out some duties remotely.

Among the work he will continue to carry out is his daily perusal of his red boxes of paperwork, containing all his documents of state. 

In a letter released shortly a week after the news was announced, King Charles thanked the British public for their 'many messages of support and good wishes'. 

He continued: 'As all those who have been affected by cancer will know, such kind thoughts are the greatest comfort and encouragement. 

'It is equally heartening to hear how sharing my own diagnosis has helped promote public understanding and shine a light on the work of all those organisations which support cancer patients and their families across the UK and wider world.

'My lifelong admiration for their tireless care and dedication is all the greater as a result of my own personal experience.'

Members of the Royal family have rallied around the King, with Prince William returning to duties after spending time caring for his wife Princess Kate.

In a separate health scare, the Princess of Wales had been admitted to The London Clinic for planned abdominal surgery, and she will not be able to perform any royal engagements until at least Easter.

The heir to the throne, 41, held an investiture ceremony at Windsor Castle earlier this month before attending London's Air Ambulance charity gala dinner later that evening.

On Sunday he attended the BAFTA awards and met with filmmakers and stars, as well as congratulating awards winners, before giving out more awards at a second investiture today.

Former Chancellor Sir Sajid Javid was also among those to be knighted by the Prince of Wales for his services to politics and public life, while Game of Thrones actress Emilia Clarke and her mother were handed MBEs for setting up a brain injury charity.

However William's father is said to be supportive of him putting his own family first, and taking time out of engagements to look after his wife and children.

It is understood he visited his father at Sandringham for a half-term holiday along with Kate and their three children, Prince George, Princess Charlotte and Prince Louis. 

A source said: 'The King adores Catherine and thinks she is doing a wonderful job. He understands that family comes first.' 

Meanwhile the King was visited in London by Prince Harry, who cleared his diary to fly over from his California home in Montecito while leaving wife Meghan Markle and his two children, Prince Archie and Princess Lillibet, behind. 

The Duke of Sussex, 39, flew to London on a commercial plane the day after the announcement, arriving at Clarence House in the afternoon.

He is then thought to have spent around 45 minutes with his father, seeing him for the first time since the late Queen Elizabeth II's funeral.

Harry is not believed to have seen his brother, with the rift between Charles' sons showing few signs of ever repairing.  

The prince then stayed overnight in a hotel before flying home the next morning. 

Meanwhile King Charles and Queen Camilla were driven straight from their meeting with Harry to Buckingham Palace, where they took a helicopter to their Sandringham estate.

Harry is expected to return to Britain in May for a service at St Paul's Cathedral to mark the tenth anniversary of the Invictus Games.

In an interview with Good Morning America this week, Harry said he was pleased to have visited the UK to see his father.

The prince, who headed to Vancouver, Canada, last week with his wife Meghan for an Invictus Games celebration, said he would return to see him again as he has other trips to the UK planned and did not discount the suggestion that his family rift could be healed by the crisis.

The King has spent the majority of time at the Norfolk residence and was seen braving the wind and rain on Sunday as he attended church with his wife.

He offered a smile and a wave out from underneath his umbrella as he arrived at St Mary Magdalene Church and smiled at wellwishers.

Queen Camilla also spoke about her husband's diagnosis during her first public engagement since the announcement.

The 76-year-old took a five-hour drive from her husband's side at Sandringham to Wiltshire's Salisbury's Cathedral earlier this month after the local helipad flooded. 

Attending a charity musical evening, the Queen said: 'He is doing extremely well under the circumstances. 

'He is very touched by all of the letters and messages the public have been sending from everywhere. That's very cheering.'

The Palace has called for the King's privacy to be respected, especially during his treatment, but said he wanted to make his diagnosis public because of his long-running support for cancer charities.

A host of medical professionals from different groups have commended the King's candour over his health.