Princess Charlotte is being christened tomorrow in front of the Queen and close family as well-wishers gather to catch a glimpse of the newest royal addition.
The Cambridges will appear in public for the first time as a family of four at the nine-week-old's baptism at the Church of St Mary Magdalene in Sandringham - walking distance from their Norfolk country mansion Anmer Hall.
Guests including the Princess's 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 will watch the traditional religious service.
The Duke and Duchess of Cambridge will also bring along toddler son Prince George, who turns two later this month.
Charlotte's godparents - most of whom are likely to be close friends of William and Kate - will be announced ahead of the service and be among the small congregation in the 16th century church.
Although the ceremony, conducted by the Archbishop of Canterbury the Most Rev Justin Welby, is private, the Duke and Duchess have agreed to allow members of the public into the area outside the church known as the paddock to see Charlotte and the royals as they make their way to and from the venue - much like the arrangements for the Christmas Day service.
Norfolk Police are expecting large crowds and urged people to arrive in time for the opening of the paddock gates at 3pm. The ceremony is due to start at 4.30pm.
Superintendent Kevin Clarke said: ''With this being such a special occasion we are expecting the area to be extremely busy on Sunday and encourage the public to heed our advice so they can enjoy the event safely.''
Car parking will be available but huge numbers of well-wishers are expected.
''People are asked to consider their arrival time carefully as they could be queuing for some time in warm temperatures with limited refreshments and facilities in the area,'' a spokesman added.
Anyone bringing flowers will be asked to give them to representatives of East Anglia's Children's Hospices (EACH), where Kate is a patron, who will then take them to hospices in the region.
A Kensington Palace spokesman said: "The Duke and Duchess are hugely grateful for the warm wishes they have received since Princess Charlotte's birth - many of them from local people in Norfolk - and are delighted the paddock can be opened on the day of the christening.''
Just like George's baptism, a number of senior royals are expected to be missing from the service. In October 2013 when George was christened at the Chapel Royal, the Princess Royal, the Duke of York and the Earl of Wessex were not among the guests.
Charlotte and George's full time live in nanny Maria Teresa Turrion Borrallo will be on hand at the church, but the Princess's uncle, Prince Harry, will miss the event, having already left to spend three months in Africa.
The ceremony has a historical link to Charlotte's late grandmother, Diana, Princess of Wales - who died in a car crash 18 years ago.
St Mary Magdalene is where Diana was christened on August 30, 1961. She was born at Park House on the Sandringham estate in Norfolk where she spent her childhood. William and Kate chose Diana as one of Charlotte's middle names in honour of the princess.
The church is used by the Queen when she is at residence on her private estate and is where the royal family worship on Christmas Day each year.
Baby Charlotte - the star guest - is likely to make a rare appearance for the cameras - only the second glimpse of the Princess in public since she was born.
Archbishop Justin will give an address. He will be supported by The Reverend Canon Jonathan Riviere, the Rector of the Sandringham group of parishes.
Mario Testino has been asked by William and Kate to take the official photographs after the service - with the Queen expected to sit for the world renowned fashion photographer for the first official time as part of the christening party.
The Peruvian - Diana's favourite photographer - has worked with William and Kate, the Prince of Wales, the Duchess of Cornwall and the late Princess before, but never done an official shoot which included the Queen.
Princess Charlotte Elizabeth Diana of Cambridge, who is fourth in line to the throne, was born on May 2 at 8.34am, weighing 8lbs 3oz.
Kate and William proudly showed their sleeping baby princess, who was wrapped in a shawl and a bonnet, to the world as they left the Lindo Wing of St Mary's Hospital, London, just hours later on the same day.
George had been to visit his new sibling earlier, but was taken home separately while his parents stayed with his sister.
Just like George, Charlotte will be christened in a replica of the intricate lace and satin christening gown made for Queen Victoria's eldest daughter, Victoria, the Princess Royal, in 1841.
Royal babies are also christened using the ornate silver gilt Lily Font which is usually on show as part of the Crown Jewels at the Tower of London.