Meghan and Harry royal wedding outfits go on show at Windsor Castle

Meghan Markle's couture wedding dress went on display at Windsor Castle on Friday in a new Relive the Royal Wedding exhibition about her May nuptials to Britain's Prince Harry.

The white, sleek long-sleeved gown with a boat neck was designed by Clare Waight Keller, the British artistic director of French fashion house Givenchy for the May 19 wedding in Windsor, an event watched by millions around the world.

Markle, now known as the Duchess of Sussex, also wore a five-metre veil decorated with hand-embroidered flowers which paid tribute to the 53 countries of the Commonwealth, as well as a diamond tiara borrowed from Queen Elizabeth II for her big day.

In accompanying audio commentary, the former actress said she had a clear idea of what she wanted to wear from the start.

"I knew at the onset I wanted a bateau neckline, I wanted a cropped sleeve, I wanted a very timeless, classic feeling," she said.

The dress also needed to be suitably modest for the wedding held in a chapel on the grounds of Windsor Castle, she said.

"There was a great level of detail that went into the planning of our wedding day," said Meghan, who is pregnant with the couple's first child.

"I think for us, we knew how large the scale of the event would be, so in making choices that were really personal and meaningful, it could make the whole experience feel intimate, even though it was a very big wedding," the duchess said.

Her full outfit, including shoes, has been put on display in a large glass box alongside an identical version of Prince Harry's wedding attire, a frockcoat uniform of the Household Cavalry, inside Windsor Castle's Grand Reception Room one of the rooms used for the wedding celebrations.

"This is a unique opportunity to see these outfits...worn on such a special day and actually in the surroundings where they were worn here at Windsor Castle," said Caroline de Guitaut, senior curator of decorative arts at the Royal Collection Trust.

Visitors can see the veil's intricate embroidery up close as well as listen to the couple talk about preparing for their wedding day through an audio device, which also has a recording of Waight Keller describing her work on the bride's dress.

"Their Royal Highnesses have been very involved in the preparation for this exhibition," de Guitaut said.

"They...wanted to be interviewed...so that they could tell the visitors all about the planning that went into their day."

Meghan described the "incredibly surreal day" when she and her fiance visited the queen, Harry's grandmother, to choose a tiara for her to wear during the wedding ceremony. She picked Queen Mary's diamond and platinum bandeau tiara from the queen's unmatched collection. It is featured in the new exhibit.

For his part, Harry said it was "very sweet" of his grandmother to lend his bride-to-be the priceless headpiece.

Also on display are the bridesmaid and pageboy outfits worn by Harry's niece and nephew, Princess Charlotte and Prince George. Charlotte's dress was also designed by Waight Keller while George's outfit is a miniature replica of Harry's uniform.

A Royal Wedding: The Duke and Duchess of Sussexopens on Friday and runs at Windsor Castle until January.