The officials spoke Thursday after a report by Britain's Daily Mail of an unusual meeting of royal household staff sparked speculation about the health of Queen Elizabeth II, 91, and her husband, Prince Philip, 95.
While few were surprised that Philip is stepping back, tourists outside the imposing gates of Buckingham Palace expressed unhappiness about the news.
The Duke has carried out 22,191 solo engagements since 1952 - so this will be an enormous change for the royal family, not least for the Queen who he has supported on so many occasions.
The prince was ill during the holiday period, while the queen, who is 91, was not seen in public for almost a month after missing church services on Christmas Day and New Year's Day because of what Buckingham Palace described as a persistent cold.
In a message from Downing Street, British Prime Minister Theresa May said she wanted to offer the country's "deepest gratitude and good wishes" to the Duke of Edinburgh following today's announcement.
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Responding to a comment from mathematician Michael Atiyah, who told him he was sorry to hear he was standing down, Philip quipped: "Well I can't stand up much longer".
"I can't stand up much longer", he joked at a reception with the Queen on Thursday.
In a statement issued about Prince Philip, who will turn 96 next month, the Royal Family said the Queen's husband would attend previously scheduled engagements between now and August, both individually and accompanying the Queen. But he will not be accepting any new invitations for visits and engagements, although he may "choose to attend" certain public events from time to time.
Alan Doyle, 47, a guide with London Tailored Tours, added: "He has supported the Queen, he's been her rock".
Elizabeth and Philip appeared to be in good health Wednesday.
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He said: "He has dedicated his life to supporting the Queen and our country with a clear sense of public duty".
She said it was time for the younger royals to step into the spotlight.
He is not expected to disappear completely from the public stage; the palace said he may still take part in some events from time to time.
Elizabeth and Philip celebrate their 70th wedding anniversary in November.
The news was announced by Buckingham Palace after a much-publicised meeting of Royal Household staff.
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Members at the event on Thursday included former Australian prime minister John Howard, TV presenter Sir David Attenborough, artist David Hockney, the former Commons speaker Betty Boothroyd and entrepreneur James Dyson.