Prince William and his wife, Kate, marked a milestone for their newborn baby Princess Charlotte on Sunday — a christening ceremony on Queen Elizabeth II’s country estate, with water brought from the River Jordan, that was steeped in royal tradition.

Hundreds of fans outside St. Mary Magdalene Church in Sandringham, a sprawling royal estate near England’s eastern coast, cheered as William and Kate arrived with toddler Prince George and 9-week-old Charlotte, who was in a vintage pram. It was only the second time Britain’s newborn princess, who is fourth in line to the throne, has been seen in public since she was born on May 2.

Charlotte was dressed for the occasion in a replica of the intricate lace-and-satin christening gown made for Queen Victoria’s eldest daughter, also named Victoria, in 1841. Until 2008, that original gown had been worn by all royal babies — including the queen — at their christenings.

Following royal tradition, holy water from the River Jordan, where it is said Jesus was baptized by John the Baptist, was used for the baptism.

Historical significance notwithstanding, the water in parts of the river may be polluted with sewage and could pose serious health risks, according to an environmental group, but the supply used for Charlotte’s christening had been sterilized.

Effluent and raw sewage have long been dumped into the lower river basin, destroying the natural habitat, the Jordanian-Palestinian-Israeli environmental activism group EcoPeace (formerly Friends of the Earth Middle East) said in a 180-page master plan, released last month. Although recent efforts have improved the water quality of the river and Israeli authorities constantly monitor the water levels for safety, the cleanliness of the water can be drastically improved.

But a Jordanian official told the BBC that the water sent for the baptism was treated and safe for use.

“We organize the process of bottling holy water from the River Jordan,” Dia Madani, head of Jordan’s baptism site commission, told the BBC

“We provide it to investors after cleaning it, sterilizing it and giving it the blessings of religious men. Each bottle has a label from the commission.”

The 16th-century church, close to William and Kate’s country house Anmer Hall, is where the royal family traditionally gathers for Christmas service. It is also where Charlotte’s late grandmother, Princess Diana, was christened in 1961.

The ceremony was private — the queen, her husband Prince Philip, Prince Charles and Kate’s family were among a small group of guests allowed inside. Guests also included five godparents that William and Kate chose for Charlotte, including William’s cousin Laura Fellowes, Kate’s cousin Adam Middleton, and three of the couple’s friends.

Fans from as far afield as Australia and the U.S. patiently lined up outside the church, hoping to get a glimpse of the baby as the royals arrive and leave.

Laurie Spencer, 52, from Florida, said she decided to give up a ticket for the British Grand Prix to be at Sandringham instead.

“When I found out the christening was happening while we were here I knew I just had to be there,” she said.

Sunday’s event saw William, Kate, George and Charlotte appear in public for the first time as a family of four. Celebrity photographer Mario Testino will take official photos of the royal family after the service.