Royal baby's place in history

The royal baby's arrival sees Prince Harry move down the line of succession from third to fourth place. The new list of succession is:

• Prince of Wales
• Duke of Cambridge
• Prince of Cambridge
• Prince Harry
• Duke of York
• Princess Beatrice of York
• Princess Eugenie of York
• Earl of Wessex
• Viscount Severn
• Lady Louise Mountbatten-Windsor
• Princess Royal
• Peter Phillips
• Savannah Phillips
• Isla Phillips
• Zara Phillips

Prime Minister David Cameron has tweeted his congratulations to the Duke and Duchess of Cambridge on the birth of their son.

The Prince of Wales was asked if there was any news as he left Harewood House, near Leeds, tonight. He laughed as he replied:

He was asked by a number of guests at the function whether he had heard anything from the hospital and he said he had not.

The birth of the Duke and Duchess of Cambridge's baby will mark the first time since 1894 that House of Windsor has three generations in line to throne at same time.

The last time this occurred, the three generations of heirs were Edward VII, George V and Edward VIII, who were in line to succeed Queen Victoria.

Read: Arbiter: 'There will be three heirs in waiting'

Under past rules, only a first-born boy of the Duke and Duchess of Cambridge would automatically have become a Prince. A daughter would have been styled Lady instead of Princess and not known as Her Royal Highness.

The Queen issued a Letters Patent under the Great Seal of the Realm when Kate was around three months pregnant declaring:

"All the children of the eldest son of the Prince of Wales should have and enjoy the style, title and attribute of royal highness with the titular dignity of Prince or Princess prefixed to their Christian names or with such other titles of honour".

When William was born he was Prince William of Wales and his children will use Cambridge in the same way, becoming HRH Prince (forename) of Cambridge or HRH Princess (forename) of Cambridge.

According to the monarchy's official website: "For the most part, members of the Royal Family who are entitled to the style and dignity of HRH Prince or Princess do not need a surname, but if at any time any of them do need a surname (such as upon marriage), that surname is Mountbatten-Windsor."

If the Duke and Duchess of Cambridge have a baby girl, she will one day become only the seventh queen to be crowned in her own right in English history.

Mary Tudor, known as Bloody Mary, was the first woman to be crowned Queen of England, rather than through marriage to a king, taking the throne in 1553 as Mary I.

Although Queen Matilda briefly ruled during the Middle Ages, she was never crowned.

Lady Jane Grey was also proclaimed Queen in 1553, but never crowned. Her reign only lasted nine days before she was imprisoned and later executed by Mary I.

If William and Kate have a first born daughter, she will eventually follow in the footsteps of Mary I, Elizabeth I, Mary II, Anne, Victoria and Elizabeth II to become monarch.

Anne - Mary II's sister - who ruled from 1702, was the first sovereign of Great Britain after England and Scotland were combined into a single kingdom.

Mary Queen of Scots was Queen in Scotland from 1542 to 1567.

A radical shake-up of the rules of succession means the Duke and Duchess of Cambridge's baby will one day become monarch - whether a boy or a girl.

Under the ancient rules of male primogeniture, first-born royal daughters in direct line to the throne were leapfrogged by their younger male siblings.

The principle was criticised and viewed as outdated and discriminatory and moves towards constitutional change gathered pace in the wake of William and Kate's wedding in April 2011 in anticipation they would produce offspring.

In October 2011, David Cameron announced that the 16 Commonwealth countries where the Queen is head of state had agreed to give female royals the same rights of succession as their brothers.

The current generation of royals will not be affected. It will not be retrospective - meaning the Princess Royal will not jump ahead of her younger brothers the Duke of York and the Earl of Wessex.

Downing Street said any attempt to alter the law would be a "difficult and complex matter", with parallel legislation needed in all such Commonwealth nations.

The Succession to the Crown Bill cleared the House of Lords in late April, after being fast-tracked through both Houses of Parliament in just three months.

It became law as the Succession to the Crown Act 2013 after being given Royal Assent on April 25 this year.

The Act will come into force once it is approved by the other Commonwealth countries where the Queen is head of state.