Meghan Markle and Prince Harry kept the guest list for very short, inviting only a small handful of their closest family and friends.
The Duke and Duchess of Sussex made the celebrations completely private in their bid to keep their son out of the spotlight.
Unlike other royal christenings, the new parents didn't invite photographers to take pictures of guests arriving at the chapel.
However some of the other guests were spotted as they drove into Windsor Castle and others have been seen in the UK in the lead up to the event, so we have some idea of Meghan and Harry's guestlist.
Kate and William were seen driving into Windsor in their car earlier today.
William, who is wearing sunglasses, was driving and Kate appeared to be wearing a blue dress.
However it looks like they've left Prince George, Princess Charlotte and Prince Louis at home.
The Duke and Duchess of Cornwall flew in to Windsor Castle in a private helicopter ahead of the celebration.
Harry and William's former nanny Tiggy Legge-Bourke was also seen driving into the castle.
Tiggy, who now lives on Glanusk Estate in Wales, cared for Princes William and Harry in the nineties and retired from her royal role in 1999 when she married former British army officer Charles Pettifer.
Earlier this week Meghan was seen at Wimbledon supporting her friend Serena with two of her university pals - Lindsey Roth and Genevieve Hillis.
It's therefore likely that they will be at the celebrations, and they could even be two of Archie's godparents.
Meghan's best friend Jessica Mulroney also made fans think she was heading to the UK with a cryptic Instagram post earlier this week.
The 38-year-old fashion stylist told her 319,000 followers : "I won't be back with my family for a while so this ends the Instagram session of mum losing her [poop-emoji]".
She deleted the post just 35 minutes later after being inundated with comments from excited royal fans.
However many members of the Royal Family and other important people in Meghan and Harry's lives missed the christening.
Neither the Queen nor Prince Philip, Archie's great grandparents, will be at the ceremony inside Windsor Castle.
This is reportedly due to a 'diary clash'.
The Queen did attend Prince George's christening in October 2013 and Princess Charlotte in July 2015, along with her husband the Duke of Edinburgh. However they missed Prince Louis's last year.
Meghan's good friend Serena Williams will also be missing the celebrations as she is playing at Wimbledon this week.
When asked if she was going after winning her second round singles match on Thursday, she said: "No, I'm working on Saturday."
All of Meghan's family - except her mum Doria - are also expected to miss the christening after their bitter and ongoing fallout.
None of her relatives were invited to her wedding and she reporedly hasn't spoken to her father Thomas Markle for months after he gave a series of embarrassing and personal TV interviews.
