The birth of a future king means a return to a "long unbroken line of male rule", a royal historian said.

Kate Williams said the British tend to prefer queens, who are often viewed as more exciting than "dreary old" kings, on the throne.

But with three generations of kings waiting in line after Elizabeth II, it could be many years before Britain sees another female monarch.

The new prince - who has been born third in line - follows two men in the line of succession - his grandfather the Prince of Wales and his father the Duke of Cambridge.

A run of four kings succeeded Queen Victoria - Edward VII, George V, Edward VIII and George VI - before the present Queen acceded to the throne.

Dr Williams said: "We'll have a long unbroken line of male rule which is what we've usually had. That's why queens really stick out."

She added: "We tend to like queens on the throne. They're often seen to have what's known as soft skills in abundance - talking to people, being polite, charming and serene.

"I think the British like it when they have women on the throne. They're different. They're exciting, instead of dreary old men."

Dr Williams said, throughout history, kings had not been perceived to be as hard working as their female counterparts.

"Queens are seen as harder working - if you compare how Queen Victoria was to her earlier predecessors. They have more to prove."

The last future king to be born was the baby's father William in 1982 and the last king to wear the crown was the baby's great great grandfather George VI.

Unlike William and Kate's son, George VI - known as Bertie to his family - never expected to be monarch, but was forced to take on the role after his brother Edward VIII abdicated.