Prince Charles visited his father, Prince Philip, in the hospital where he's been for 4 nights

• Prince Philip has been at the King Edward VII Hospital in London since Tuesday evening.
• Prince Charles, the oldest son of the Queen and Prince Philip, visited the hospital Saturday.
• The 99-year-old duke is at the hospital as a "precautionary measure" after feeling unwell.

Prince Charles on Saturday visited King Edward VII Hospital in London, where his father, Prince Philip, has been staying since Tuesday evening, a Buckingham Palace spokesperson confirmed to Insider.

The Duke of Edinburgh, the 99-year-old husband of the Queen, was admitted to the hospital after feeling unwell under guidance from his doctor.

On Wednesday, a statement from Buckingham Palace obtained by Insider said that the duke was staying a second night in the hospital as a "precautionary measure."

Chris Ship, ITV News' royal editor, shared video footage on Saturday of the Prince of Wales arriving at, and later, leaving, the London hospital.

Speaking with Insider, a Buckingham Palace spokesperson on Saturday declined to provide an additional update on Prince Philip's status, but referenced a statement issued Wednesday saying that the duke was staying a second night in the hospital as a "precautionary measure."

"His Royal Highness The Duke of Edinburgh was admitted to the King Edward VII Hospital in London, on Tuesday evening. The Duke's admission is a precautionary measure, on the advice of His Royal Highness's Doctor, after feeling unwell," the palace spokesperson said. "The Duke is expected to remain in hospital for a few days of observation and rest."

The duke's condition is unrelated to COVID-19, royal correspondent Victoria Murphy reported on Wednesday.

The King Edward VII Hospital's website states that visitors are "only considered in exceptional circumstances" due to the ongoing COVID-19 pandemic.

"One visitor will be permitted to visit. No children will be permitted to visit. The health, safety and well-being of our patients, family, carers and staff remain our absolute priority," according to the hospital's guidelines.

On Thursday, a royal source told The Sun's royal correspondent Matt Wilkinson: "The Duke is in good spirits."

Representatives for the Prince of Wales did not immediately respond to Insider's request for comment.