Kate Middleton admitted to hospital in early stages of labour

Kate Middleton was today admitted to a leading hospital here in the early stages of labour to deliver her and Prince William's third child, Kensington Palace announced.

Kate and William are expecting their third child, after Prince George and Princess Charlotte. The fifth-in-line, Royal baby will be Queen Elizabeth II's sixth great-grandchild.

"Her Royal Highness The Duchess of Cambridge was admitted to St Mary's Hospital, Paddington, London earlier this morning in the early stages of labour. The Duchess travelled by car from Kensington Palace to the Lindo Wing at St. Mary's Hospital with The Duke of Cambridge," the Palace said in a statement.

The countdown to the royal baby began earlier this month as barriers and parking restrictions sprung up at the London hospital where the new-born is to be welcomed.

The Palace had not revealed the baby's due date but it was expected that notices would go up around St Mary's Hospital in Paddington a couple of weeks before the birth, planned at the Lindo Wing where Kate gave birth to George and Charlotte.

The yellow notices put up outside the Lindo Wing refer to an "event" and suspended parking on the street from April 9 until April 30.

Some reports had been speculating on the due date being today but Kate has gone beyond her due date for both her previous pregnancies George in 2013 and Charlotte in 2015 leading to what was dubbed as the "Great Kate Wait".

The new child will be fifth in line to the British throne, behind big sister Charlotte and pushing uncle Prince Harry one place down the line of succession to sixth. He or she will be the sixth great grandchild of Queen Elizabeth II, who celebrated her 92nd birthday on Saturday.

A change in the law after William, 35, Kate, 36, were married in April 2011 gave female heirs the same rights of accession to the throne in the UK as men.

Kate suffered from hyperemesis gravidarum, or severe levels of nausea and vomiting, during the early stages of her pregnancy during all three births.

A formal signed bulletin will be placed outside Buckingham Palace announcing the news of the new-born after William has informed his grandmother, Queen Elizabeth II, and other members of the royal family once the baby is born.

Britain's royal gynaeologist Guy Thorpe-Beeston will be present for the birth.

As with both previous births, media positions are clearly marked on the pavement opposite the Lindo Wing doors where Kate and husband William will emerge with their new arrival.

William and Kate have chosen not to find out if they are having a boy or girl, but bookies are favouring a girl.

For a girl, the favourite names are Alice, Mary, Victoria and Alexandra, with Albert, Arthur, Frederick and James as the top choices for a boy.