King Charles is "hugely positive" following his cancer diagnosis as the disease was "caught early", according to royal sources.
The King was reported on Monday to be in good spirits following the surprise news he was diagnosed with cancer.
Family and friends were impressed by the monarch's determination to continue with "business as usual".
King Charles's condition, according to reports in The Mail, has been caught very early and the "prognosis is good".
King Charles has been diagnosed with a form of cancer
PA
Buckingham Palace disclosed that doctors had found an unspecified form of cancer during treatment for a benign enlarged prostate.
King Charles informed his close family by phone, including his younger son Prince Harry.
The Duke of Sussex will soon fly back from his home in California to see his father.
It is not known where the duke will stay when he visits the UK, as he needs permission from Buckingham Palace to stay on a royal estate.
Harry is travelling to the UK to visit his fatherReutersThis comes after Harry, 39, and his wife Meghan Markle, 42, were evicted from their UK home Frogmore Cottage last year.
Prince Harry returned the keys to Frogmore Cottage last June when the Sussexes vacated the property.
His request to stay at Windsor Castle was refused by the Palace when he last visited the UK in September.
Consequently, Prince Harry ended up staying in a hotel.
Queen Camilla performed daily duties last week providing updates on the King's health
ReutersLATEST ROYAL NEWS:
King Charles has cancer, Palace confirms in a statementPAKing Charles arrived in London on Monday morning after travelling from his Sandringham estate with his wife Camilla.
The King will start outpatient treatment at an undisclosed hospital, meaning he will not stay overnight.
Queen Camilla, 76, will be at her husband's side throughout but has insisted on continuing her public engagements.
Other members of the Royal Family will be stepping up to stand in for the sovereign, including Prince William, 41, who will return to duties on Wednesday.
The Prince of Wales temporarily stopped royal duties while his wife, Princess Kate, recovered from "planned abdominal surgery".