Prince Philip has been married to the Queen for more than 71 years (Picture: Crown Copyright).
The Duke of Edinburgh, the longest-serving consort in British history, is celebrating his 98th birthday.
Gun salutes were fired in his honour by The King's Troop Royal Horse Artillery in London's Hyde Park at noon.
Honourable Artillery Company then fired a 62-gun salute at Gun Wharf at the Tower of London.
"A very Happy Birthday to His Royal Highness Prince Philip, Duke of Edinburgh, who is 98 today," the Army said in a tweet.
Buckingham Palace, Kensington Palace, Clarence House and the Duke of York's official Twitter accounts also marked the occasion by sending birthday wishes to the royal patriarch.
Prince Philip has been married to the Queen for more than 71 years.
While the Queen had a busy set of engagements last week, the Duke, who retired from public duties in 2017 after decades of royal service, did not take part in the official events as part of the US state visit and did not meet US President Donald Trump behind the scenes.
Prince Harry was formally appointed as Captain General Royal Marines in December 2017, succeeding his grandfather the Duke of Edinburgh.
Prince Philip mostly stays at Wood Farm on the Sandringham estate in Norfolk, where he busies himself by reading, painting, meeting friends and staying active.
He still enjoys carriage-driving and was seen at the reins at the Windsor Horse Show in May.