King Charles waves to royal fans as well-wishers cheer for the monarch amid his cancer treatment

King Charles III has been spotted waving to royal fans as he left Clarence House in London today. 

The monarch was pictured greeting well-wishers outside the royal residence as he was driven out in his state Bentley limousine.

It is not known where His Majesty, who wore a grey suit and blue tie, was going at the time and he was not accompanied by the Queen.  

The King is currently being treated for an undisclosed form of cancer after being diagnosed with a large prostate earlier this year. 

It comes as the Charles yesterday greeted the governor of the Bank of England for a historic meeting where he was presented with the first banknotes bearing his portrait.

The King praised the notes as 'very well designed' and expressed his surprise at being only the second monarch to feature. 

He received a leather-bound booklet containing the historic legal tender from Andrew Bailey at Buckingham Palace.

It was a milestone moment for the monarch, who is undergoing treatment for an undisclosed cancer.

'Good morning Governor. I'm sorry it's a bit delayed this. I hope it isn't too delayed,' Charles said.

But Mr Bailey replied: 'Not at all. We're still in advance of launching them.'

Charles remarked: 'Oh you are? Great.'

Charles and Mr Bailey were joined by Sarah John, the Bank of England's Chief Cashier, whose signature appears on the currency, and the King gave a broad grin as he greeted his guests in the 1844 Room. 

Ms John told the King they were the number 1 notes in the series and that the general public would start to see them early in June.

The King replied: 'I wondered how it would come out.'

Charles inspected the four £5, £10, £20 and £50 notes - the first low-numbered note of each denomination with 01 000001 serial numbers - and pointed and smiled at the details as Mr Bailey turned the pages, showing the front and back.

King Charles is only the second British monarch to grace the Bank of England's notes - and it is the first time one sovereign's image has been replaced with another