The Prince of Wales, Prince Charles, on Saturday visited a London hospital where his father, the Duke of Edinburgh, Prince Philip, is admitted after feeling unwell.

99-year-old Prince Philip was admitted on Tuesday as a "precautionary measure" after feeling unwell.

Reports indicate the ailment is not related to COVID-19, but Prince Philip is expected to remain in hospital until next week.

Reuters reports that doctors were acting out of an abundance of caution and the duke remains in good spirits.

Both Philip and 94-year-old Queen Elizabeth II received their first doses of the COVID-19 vaccine in January.

Buckingham Palace announced at the time that Prince Philip and the Queen had received the vaccinations from a household doctor at Windsor Castle.