Meghan Markle sought comfort in her prince and his brother on Christmas Day as she pulled off her first public appearance with the Queen and curtsy as a soon-to-be member of the royal family.
With an unsure smile and a firm grip on Harry's arm, the Californian actress emerged from St Mary Magdalene Church in a huddle of future in-laws.
As the Queen led the charge with Prince Philip standing closely behind, Markle stayed in her lane next to Prince William and her fiance.
Unversed in the Sandringham Christmas Day order of events, Markle, 36, was put at ease by Harry and William who seemed to offer words of encouragement and pointers as they left the church, the Daily Mail reports.
Markle was elegant in a wide collar, camel wrap coat by Canadian luxury brand Sentaler. It tapered in around the waist and flared out at the hem, for the St Mary Magdalene Church Christmas service.
Matching her camel coat with a chestnut-brown felt hat, Meghan wore a pair of coordinating £630 ($1200) Stuart Weitzman's Hiline high-heeled suede boots.
Markle gave her curtsy as the Queen departed. Kate also curtsied, while Will, Harry and the vicar all bowed their heads toward the Queen.
Markle and the Queen met privately with Harry before their engagement was announced but had not been seen together by others until today.
And despite the training and etiquette tips she has no doubt revised since accepting Harry's proposal and her experience in the spotlight as an actress, the star appeared nervous as she waited for the big moment.
When the time came, Markle dipped emphatically with her head bowed, giving a wholehearted effort as the crowds watched.
Quickly springing upright again, barely a second went by before her gloved hand was reaching for Harry's arm again.
Once interlinked, he led her to a wheelchair-ridden well-wisher who had waited in the cold to wish the couple a Merry Christmas.
The pair then accepted bouquets from fans as they walked back to Sandringham House.
Markle, with her first curtsy behind her and a day of formal festivities ahead, seemed to loosen up as she greeted and accepted gifts from well-wishers.
She completed her look with a £900 round handbag in brown leather and caramel suede with a gold coloured handle made by Chloe, while a pair of Maison Birk diamond earrings added a touch of sparkle to Markle's classy ensemble.
They are the same £3500 Snowflake design earrings she wore to her Buckingham Palace dinner last week.
It is thought her brown hat may be a Jane Taylor piece, a milliner popular with Kate.
It is the first time Markle and Kate have been pictured together since Markle and Prince Harry revealed their impending nuptials.
Kate is pregnant with her third child and showed off a small baby bump beneath a striking £2655 tartan Miu Miu coat.
The Queen arrived at the service later by car wearing an eye-popping orange jacket with a matching intricate floral hat.
As they made the return journey to Sandringham House after the service was over, Markle and Harry stopped to chat to some of the crowd who turned out to see them attend church.
Among them was Judith Wallis, who was sitting in a wheelchair and is staying at the neighbouring Park House Hotel on her first Christmas Day visit to Sandringham.
She said Harry recognised her teddy bear called Maureen, which is a mascot for Armed Forces charity SSAFA, and her hat, which bore the Gurkha regiment emblem.
She said Markle spoke to them too and was "very very lovely".
Tess Gilder, manager of Park House, which describes itself as a unique hotel for disabled people, was with Wallis. She said of Markle: "She was just so natural, so lovely."
She added: "I think they just wished us a Happy Christmas and were interested in whether we had been before."
Emily Randall, 31, was first in the queue to get into the area by the church with her boyfriend Jamie Mackay, 42.
She said they set out from Chichester in Sussex before 10pm on Christmas Eve and arrived at Sandringham around 2am.
She said: "We thought it would be really busy. We looked online. We were the first ones here camping in the dark for two hours."
She said they had missed the Queen when she visited Chichester, so decided to make the trip to Sandringham.
Back at Sandringham House, the royal Family traditionally indulge in turkey, reared at Sandringham, before settling down to watch TV, including the Queen's Christmas speech.
This year, it is understood that Prince Harry and his fiancee will stay with Prince William and the Duchess of Cambridge Kate at Anmer Hall, their home in the Sandringham grounds, rather than in the main house.
Markle will have to adjust to the royal family's idiosyncratic ways and customs, ingrained in centuries of tradition.
The royals exchange gifts on Christmas Eve, in keeping with German practice.
Markle is reportedly an animal lover but will have to put up the with royals' tradition of going shooting on Boxing Day.
The Queen arrived in a car and joined the group, which also included the Duke of Edinburgh and the Prince of Wales.
Hundreds of well-wishers turned out to catch a glimpse of the royal family, and some called out "Merry Christmas" as they walked past.
Prince Philip led the charge with Prince Charles following closely behind. He walked with his wife Camilla who wore a scarf to cope with the cold.
Prince Philip's other sons Andrew and Edward were accompanied by their sister Princess Anne who sported a royal purple shawl with a hint of festive red over a deep blue coat.
But not all of the family were dressed so spectacularly: Princess Beatrice opted to shun high heels for a pair of dirty trainers - leaving her father the Duke of York looking distinctly unimpressed.
The royal family appeared to be in markedly higher spirits this morning compared to last year when the Queen was forced to miss the service while recovering from a heavy cold.
She and the Duke of Edinburgh had delayed their trip to the private Sandringham estate by a day after they became ill.