Prince Charles was asked to visit his father in hospital to discuss the future, according to reports.
Prince Philip, 99, reportedly called for his son to attend the hospital to talk of the Royal Family's future.
The Duke was initially due to spend a few days under medical care for "observation and rest" the King Edward VII's Hospital for an undisclosed reason.
Prince Philip attended the London hospital last Tuesday evening as a precautionary measure after feeling unwell.
Former Buckingham Palace official Dickie Arbiter claimed Prince Philip may have requested the visit from son Charles last Saturday as he prepares for him to take over the family, Birmingham Live has reported.
Speaking on True Royalty TV's weekly The Royal Beat programme earlier today, Mr Arbiter said: "He was just saying to Charles, 'one day you are going to be the leading man of the family'."
Mr Arbiter told The Royal Beat: "I think it was at the request of the Duke that the Prince of Wales visited.
"To lay the ground. Look the man is 99, he is in with an infection.
"My guess is that he will come out, he will walk out and he will go back to Windsor.
"But eventually he is going to die and he was just saying to Charles, ‘one day you are going to be the leading man of the family’".
Members of the royal family have continued with their duties since the duke was taken to hospital after telling his doctor he felt unwell.
The morning after Philip was admitted, Charles and the Duchess of Cornwall - who have received their Covid jabs - visited the Queen Elizabeth Hospital in Birmingham to learn about vaccination trials.
