Royal baby: Duchess of Cambridge admitted to hospital in 'early stages of labour'

The Duchess of Cambridge is in hospital in the early stages of labour, Kensington Palace announced this morning.

Kate Middleton travelled with her husband, the Duke of Cambridge, to St Mary's Hospital in central London early on Monday.

The Duchess of Cambridge has been on maternity leave since attending a charity lunch in London on March 22.Reuters/Peter Nicholls

It is not known whether the baby, who will be fifth in line to the throne, is a boy or a girl. Kate is hoping for a natural birth as she had with her first two children, George and Charlotte.

Bookies' favourites for boys' names are Arthur, Philip and Albert, while Victoria, Alice and Mary are the top choices for a princess. All are highly traditional royal names and it is thought the couple will not opt for a more modern option reflecting the Middleton side of the family.

The pregnancy was first announced in October and if born today the royal baby would celebrate a birthday on St George's Day.

It is highly unlikely the baby, as the third child, would ever accede to the throne. It is yet to happen in the current House of Windsor and the last time it happened was when the third child of George III and Queen Charlotte, William IV, became king and ruled from 1830 to 1837.

Under previous rules however, if the baby were a boy he would have leapfrogged over his older sister Charlotte to become fourth in line to the throne. But the Succession to the Crown Act 2013 removed the automatic preference for male offspring, meaning royal children now inherit the throne in strict order of birth.