Philip was so busy he even managed to miss a band playing Happy Birthday during the changing of the guard at Buckingham Palace.
The Prince kicked off the day with a presentation to the Institution of Mechanical Engineers before heading to a reception for winners of the gold standard of the Duke of Edinburgh's Awards. After lunch he was at an event to promote the British tourist industry before putting in an appearance at another awards ceremony and a reception for the British Boat Service Association.
Despite his advancing years, the Queen's spouse - who last year became the longest-serving consort in British history - remains sprightly and in good health. He made a full recovery from a recent back problem and was recently seen nimbly vaulting a fence at the Windsor Horse Show.
Perhaps contributing to youthful approach is the strong work ethic he shares with the monarch. Last year he completed more than 350 official engagements.
Prince Philip wasn't the only European royal celebrating a birthday this week. Denmark's Prince Henrik, who turns 75 on Thursday, marked his milestone a day early with his wife Queen Margrethe and their family in Copenhagen.
The Danish royals, including Henrik's sons Crown Prince Frederik and Prince Joachim along with their wives Crown Princess Mary and Princess Marie, boarded the royal yacht Dannebrog for a spot of lunch. Also accompanying them was Henrik's pet dachshund Vega.