Princess Charlotte was pushed to her christening in a vintage pram the Queen used for two of her own children as the world was given their first glimpse of the Cambridges as a family of four.
The Duke and Duchess of Cambridge delighted well-wishers by walking from nearby Sandringham House with toddler Prince George and nine week-old Charlotte, who was dressed in the elaborate cream lace and satin royal christening gown, to the Church of St Mary Magdalene.
Kate pushed the Millson pram - once used for the Duke of York and the Earl of Wessex - while William held George's hand as the prince, who is nearly two, waved at the crowds.
It is only the second time the baby princess has been seen in public and the first time the family has appeared all together for the cameras.
Charlotte is being baptised by the Archbishop of Canterbury the Most Rev Justin Welby in a private service in front of just 21 guests, including great-grandparents the Queen and the Duke of Edinburgh, grandparents the Prince of Wales and Carole and Michael Middleton, step-grandmother the Duchess of Cornwall and Kate's siblings Pippa and James Middleton.
Her five godparents were also among the tiny congregation. They are Diana, Princess of Wales' niece and William's cousin the Hon Laura Fellowes; Kate's cousin Adam Middleton; Sophie Carter - a long term confidante of Kate's; William's Eton school friend James Meade; and one of his best friends since childhood Thomas van Straubenzee.
Crowds of royal fans some of whom camped out overnight - founds spots inside the paddock - the name given to the area outside the Norfolk church after William and Kate gave permission for the area to be open to the public - just like when the royals visit on Christmas Day.
Prince Harry was missing from the event, having already left to spend three months in Africa, and other senior royals the Duke of York, who is abroad, Anne and the Earl of Wessex were also absent from the congregation just as they were from George's baptism.
Princess Charlotte Elizabeth Diana of Cambridge was born on May 2 at 8.34am, weighing 8lbs 3oz.
Charlotte's gown is a replica of the intricate lace and satin christening gown made for Queen Victoria's eldest daughter, Victoria, the Princess Royal, in 1841. The original is now too delicate to wear.
She is being baptised using the ornate silver gilt Lily Font which is usually on show as part of the Crown Jewels at the Tower of London.
Afterwards, guests will gather at Sandringham House for tea hosted by William and Kate, when they will be served slices of christening cake, taken from a tier of their wedding cake. Celebrity and fashion photographer Mario Testino will take the official pictures.
As George entered the churchyard, he let go of William's hand and made his own way through the grounds.
Charlotte could be heard crying as they approached the church door with Kate having to pick her up to settle her. Meanwhile, inquisitive George took matters into his own hands and tried to make his way into the church by himself.
Kate was dressed in an ivory Alexander McQueen outfit with Jane Taylor hat.