Kate Pregnant: Making A Happy Royal Family

Before their wedding, the Duke and Duchess of Cambridge made no secret of the fact they wanted to have children.

Kate, who is close to her own immediate family, said: "I hope we will be able to have a happy family ourselves."

William also expressed his desire to have children, and there was plenty of speculation that the Duchess was feeling broody.

And reports they included Brussels sprouts on the food order for their honeymoon in the Seychelles led to suggestions she was on a diet aimed at boosting her folic acid intake in anticipation of conception.

The baby will be Carole and Michael Middleton's first grandchild and the first for the Prince of Wales - although he is already a grandfather to the Duchess of Cornwall's grandchildren.

He or she is destined to be King or Queen and will be born third in line and in direct succession to the throne - knocking Harry down to fourth.

Prime Minister David Cameron announced in October last year that the 15 other Commonwealth countries where the Queen is Head of State had agreed to give female royals the same rights of succession as their brothers.

"Put simply, if the Duke and Duchess of Cambridge were to have a little girl, that girl would one day be our Queen," Mr Cameron said.

When the law is enacted, first-born royal daughters in direct line to the throne will no longer be leapfrogged by their younger male siblings.

The proposed constitutional change was spurred by the marriage of the Duke and Duchess of Cambridge in anticipation that they would produce a child.

He or she will one day be Head of the Armed Forces, Supreme Governor of the Church of England and Head of the Commonwealth, which covers 54 nations across the world, and subsequently Head of State of 16 countries.

The birth will also expose the Cambridges, already famous around the world, to even higher levels of public fascination.

William and Kate will have to balance protecting their prince or princess with meeting the the nation's insatiable desire to know more about its future ruler.

When William was born in June 1982, thousands gathered outside Buckingham Palace to wait for the birth to be formally announced.

He was the first future British King to be born in a hospital, showing how times had changed down the generations.

His grandmother, Queen Elizabeth II, was born in her grandparents' London home in Mayfair.

At the time Home Secretary Sir William Joynson-Hicks waited in the next room as part of an age-old tradition designed to prevent a substitute baby being smuggled in.

Kate will no doubt be glad the custom has since been discontinued.