Kate and William debut beautiful baby girl (Pictures of the new Princess)

Kate Middleton stepped out of the private Lindo Wing at St. Mary's Hospital, 12 hours after being admitted and 10 hours after giving birth, with the new Royal Baby Girl.

The Duchess of Cambridge looked immaculate and in happy spirits, dressed in a bright yellow and white Jenny Packham printed dress, styled with beige pumps.

Kate, whose new born daughter is fourth in line to the British throne, appeared gorgeous with her brunette hair in soft curls and a healthy flush of colours on the cheeks.

On her side was her husband, Prince William, who was also all smiles with their new princess.

The Royal Couple posed for cameras and debuted their chubby cheeked daughter, who is yet to be named, on the steps of the Lindo Wing.

The adorable Princess was born at 8:34 am this morning and weighs 8lbs and 3oz. She was dressed in a yellow bonnet with a white blanket draped over her as she gave her first glimpse to the world.

Kate held on tightly to the new born and posed for the awaiting photographers before making her way to Kensington Palace.

Earlier, 21 months old toddler Prince George was seen arriving to meet his baby sister alongside their proud father.