The Duchess of Cambridge is pregnant, and is in hospital with morning sickness.
Robert Hardman, Daily Mail writer and author of Our Queen, and Kate Williams, historian and author, discuss, with three generations potentially now in line to the throne, if this will ever again be a country with a young monarch and will we instead move into an era of elderly kings and queens with brief geriatric rule?
Talking to the Today programme's Sarah Montague, Ms William's explained that "It looks like a line of dominos in waiting... she or he might rule into the 22nd century."
"It's not just our monarch, our nation is changing... we are becoming much more age-heavy," she added.
Mr Hardman said "I can safely say that I have seen my last diamond jubilee."
"We are talking about a series of silver thrones."
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