When Kate Middleton returns to north Wales with Prince William next week, she will begin married life with the knowledge that whatever roles she takes on, she has one definite responsibility - producing an heir.
"If Kate is not pregnant in the next nine months, she will be defying 200 years of royal tradition," said Andrew Morton, a biographer of William's late mother Diana who has just written a book about the newlyweds.
After years of waiting for her prince to propose, the 29-year-old will be expected to move quickly to produce an heir for the second-in-line to the throne, to ensure there is no break in the line of succession.
Her predecessors certainly wasted no time.
William was born barely 11 months after his mother Diana married his father Prince Charles in 1981.
And Charles himself, the heir to the throne, was born almost exactly a year after his parents Queen Elizabeth II and Prince Philip married in 1947.
Asked about his plans for children in an interview in November to mark his engagement, William said: "I think we'll take it one step at a time. We'll sort of get over the marriage first and then maybe look at the kids."