So why has Prince Philip chosen to retire?
When most people retire in their mid-sixties, it's quite something that the Duke of Edinburgh left it until his mid-nineties to announce he will step down from royal duties.
What that means is he will have no formal engagements in his diary from this Autumn.
And so for the first time in 70 years he will not have an official programme as the husband of first Princess Elizabeth and then Queen Elizabeth II.
So what changes?
From now own - Buckingham Palace says 'Team Windsor' will be stepping up.
So you will see the Queen on visits with other members of the royal family.
You will see the Queen doing visits alone.
And you will see other family (Charles, Anne, Andrew, Edward) doing more.
Interestingly, there is a synergy of timing here.
As Prince Philip steps out of public life, his grandson Prince William will become a 'full-time royal'. He is giving up his job as an air ambulance pilot in East Anglia and will move back to London in September.
The Queen, however, will not be stepping down. Her engagements will continue as plannned.
And nor does the Monarch intend to do something similar in the future.
Buckingham Palace will remind you of the speech, Princess Elizabeth gave in Cape Town in 1947: "I declare before you all that my whole life whether it be long or short shall be devoted to your service and the service of our great imperial family to which we all belong."
This decision to retire has been described as a 'personal one' which the Duke took himself with the Queen's support.
It was made in recent months after some significant milestones in recent years: the Queen becoming the longest serving Monarch in British history, and her 90th birthday last year.
As for why it was announced today?
It was a day when politics must take a back seat while voters in England, Scotland and Wales go to the polls in local and mayoral elections.
And the Duke's diary for the Autumn is planned about now - and the Palace was starting to decline invitations.
Yes, it allowed speculation to mount overnight that there was a serious announcement to make about his health, but Buckingham Palace wanted to inform staff first - which they did at 10 o'clock this morning.
All the staff from Buckingham Palace were there and some were brought in from Windsor.
Staff in the Queen's other residences at Balmoral and Sandringham were informed locally.
But after 70 years supporting the Queen - since their marriage in 1947 - the Duke is stepping out of British public life.