previously reported.
It comes as...
Philip, 99, was admitted to King Edward VII's Hospital in London on Tuesday evening as a precautionary measure after feeling unwell. The duke is said to have walked in unaided.
On Friday, a source said: "Following consultation with his doctor, the Duke of Edinburgh is likely to remain in hospital for observation and rest over the weekend and into next week.
"As we have said previously, the doctor is acting with an abundance of caution. The duke remains in good spirits."
Harry's reported call back to the UK from his new home in the US comes after he and Meghan Markle officially quit the Royal Family.
The couple stated "service is universal" as they confirmed the move - losing their honorary titles - with the Royal Family left reeling.
The announcement came just days after it was announced a special prime-time interview with the couple and Oprah Winfrey would be aired next month.
And just last week the couple confirmed they were expecting another baby.
Prince Charles was the first member of the royal family to visit Prince Philip - making the 200-mile round-trip from his home in Highgrove, Gloucestershire, on Saturday afternoon.
It is understood that Charles wanted to visit his father due to Philip's extended stay.
The prince arrived in a grey Tesla car at around 3.20pm on Saturday and got out of the vehicle wearing a face mask, before leaving the hospital around 30 minutes later.
A Clarence House spokesman confirmed he returned to Highgrove following his visit.
It is thought Charles had not seen his father since before Christmas because of the nationwide coronavirus restrictions, with the duke staying at Windsor Castle with the Queen.
The duke, who will turn 100 on June 10, is in hospital for an undisclosed reason, although it is not coronavirus-related.
The hospital's website states visitors will "only be considered in exceptional circumstances".
Philip is known for his "no fuss" attitude.
Ahead of Christmas, the duke released a rare public message praising teachers and school staff for their efforts teaching the nation's children during the pandemic.
He retired from his public duties at the age of 96 in 2017 after 65 years of public life.
Since 1952 he attended 22,219 solo engagements and 637 overseas tours in a career marked by his famous gaffes.
Prince Philip, 99, expected to remain in hospital for 'observation and rest' into next week