London (CNN) Britain's Prince Harry and the American actor Meghan Markle have described their joy at the prospect of getting married, hours after their engagement was announced on Monday.

In a brief appearance in the Sunken Garden at Kensington Palace, Harry told reporters he knew Markle was "the one" from "the very first time we met."

The prince declined to elaborate on his proposal to Markle, but when asked whether it was romantic, he smiled and said, "of course it was."

Prince Harry and fiancée Meghan Markle pose for photographers after their engagement was announced Monday.

The pair appeared overjoyed as they appeared for photographers on a slightly overcast Monday afternoon in London.

Markle said she was "so very happy" and flashed her engagement ring to reporters.

The ring, designed by Harry, has a gold band and features a large diamond from Botswana and two smaller outer diamonds from the personal collection of Harry's late mother, Diana, Princess of Wales, according to a statement from Kensington Palace.

Botswana holds special significance for the couple, who have spent time together there over the past year and a half, Kensington Palace said.

Harry designed the engagement ring which was made by Cleave and Company, Court Jewellers and Medallists to Her Majesty The Queen.

The pair, who became engaged quietly earlier this month, will marry in spring 2018 and live at Nottingham Cottage at Kensington Palace, where Harry currently lives.

Markle will be the first American to marry a British royal since the marriage of Wallis Simpson to King Edward VIII, a union so controversial that he was forced to give up the throne in December 1936 to go through with it.

Monday's announcement was made by Harry's father, Prince Charles, in a statement released from his office at Clarence House.

Prince Charles said he was "delighted to announce" the engagement, adding that Harry had informed "The Queen and other close members of his family."

The Prince of Wales is delighted to announce the engagement of Prince Harry to Ms. Meghan Markle. pic.twitter.com/zdaHR4mcY6 — Clarence House (@ClarenceHouse) November 27, 2017

"Prince Harry has also sought and received the blessing of Ms. Markle's parents," the statement added.

The couple went before photographers on Monday afternoon before taking part in a broadcast interview which will air in the evening.

Harry's grandparents, Queen Elizabeth II and her husband Prince Philip, are "delighted" for the couple and "wish them every happiness," a Buckingham Palace spokesman said.

The palace did not say what titles would be conferred upon the couple when they are married, but the prince is likely to be awarded a dukedom, meaning Markle would become a duchess. Markle will not become a princess in her own right: only daughters of royals can claim such status.

Prince Harry and Meghan Markle at the Invictus Games 2017.

Shortly after the announcement, Kensington Palace released a statement on behalf of Markle's parents, Thomas Markle and Doria Ragland.

"We are incredibly happy for Meghan and Harry. Our daughter has always been a kind and loving person. To see her union with Harry, who shares the same qualities, is a source of great joy for us as parents.

"We wish them a lifetime of happiness and are very excited for their future together," the statement ended.

Ms. Markle's parents, Mr. Thomas Markle and Doria Ragland have wished the couple 'a lifetime of happiness.' pic.twitter.com/H4kpTgpkYE — Kensington Palace (@KensingtonRoyal) November 27, 2017

Harry's brother, William and his wife, Catherine, who also reside at Kensington Palace, shared their joy at the impending union on Monday.

"We are very excited for Harry and Meghan. It has been wonderful getting to know Meghan and to see how happy she and Harry are together," they said in a statement.

Monday's announcement ends persistent speculation over when the 33-year-old prince -- who is now fifth in line to the British throne -- would propose to the actor.

Harry and his fiancée made their first public appearance as a couple in September at the Invictus Games in Toronto.

The pair were introduced in July 2016 by mutual friends in London, Markle confirmed in September. Markle is best known for her role on TV show "Suits" as well as her philanthropic work.

The 36-year-old LA native spoke of her royal relationship for the first time earlier this year telling Vanity Fair: "We're two people who are really happy and in love."

Photos: Who is Meghan Markle? Meghan Markle visits AOL Studios in New York in March 2016. Markle, a former actress, is best known for her role as Rachel Zane in the hit TV series "Suits." Her engagement to Britain's Prince Harry was announced in November. Hide Caption 1 of 15 Photos: Who is Meghan Markle? Markle attended Immaculate Heart High School, a private, all-girls Catholic school in Los Angeles. At the time she went by her first name, Rachel. Meghan is her middle name. Hide Caption 2 of 15 Photos: Who is Meghan Markle? Markle attends the Some Kind-a Gorgeous Style and Beauty Lounge at the Chateau Marmont in Los Angeles in August 2010. Hide Caption 3 of 15 Photos: Who is Meghan Markle? Markle was married to film producer Trevor Engelson for two years before they divorced in 2013. Hide Caption 4 of 15 Photos: Who is Meghan Markle? Markle appears in the TV series "Suits" with her on-screen father, played by actor Wendell Pierce. Hide Caption 5 of 15 Photos: Who is Meghan Markle? Markle addresses a United Nations conference on International Women's Day in March 2015. "I'm proud to be a woman and a feminist," said Markle, who was named the UN Women's Advocate for Political Participation and Leadership. Hide Caption 6 of 15 Photos: Who is Meghan Markle? Markle plays Kirsten in the 2015 movie "Anti-Social." Hide Caption 7 of 15 Photos: Who is Meghan Markle? Markle hosts the Women in Cable Telecommunications Signature Luncheon at McCormick Place in Chicago in May 2015. Hide Caption 8 of 15 Photos: Who is Meghan Markle? Markle attends the CFDA/Vogue Fashion Fund Awards in New York in November 2015. Hide Caption 9 of 15 Photos: Who is Meghan Markle? Markle visits Rwanda in January 2016. She went to the African country with World Vision Canada. Hide Caption 10 of 15 Photos: Who is Meghan Markle? Markle poses for a portrait in Toronto in April 2016. Hide Caption 11 of 15 Photos: Who is Meghan Markle? Markle and Crystal Valentine speak during Glamour's College Women of the Year Awards in April 2016. Hide Caption 12 of 15 Photos: Who is Meghan Markle? Markle appears on the cover of Vanity Fair in September 2017. In an accompanying interview, Markle first spoke publicly about her relationship with Prince Harry. Hide Caption 13 of 15 Photos: Who is Meghan Markle? Markle attends the Invictus Games with Prince Harry in September 2017. Hide Caption 14 of 15 Photos: Who is Meghan Markle? Markle and Prince Harry pose for a photo at Kensington Palace following the announcement of their engagement on November 27. Hide Caption 15 of 15

Markle, who has been previously married, spoke candidly about the media attention that comes with dating a member of the British royal family, saying it has its "challenges" before adding that she has her "boyfriend's support."

Separately, Prince Harry confirmed the couple were an item last November in a Kensington Palace statement criticizing the "wave of abuse and harassment" his then-girlfriend had faced from media outlets.

The palace rarely puts out such statements, only doing so in recent years to keep the paparazzi from getting too close to Prince George and Princess Charlotte, the children of Harry's brother, Prince William.

The brothers have been much more open about their personal lives than other members of the royal family. In recent months, they spoke publicly about their mother, Princess Diana, on the 20th anniversary of her death

Prince William and Catherine, Duchess of Cambridge drive from Buckingham Palace in a decorated sports car on April 29, 2011 in London, England.

Monday's announcement sets the stage for the most anticipated royal wedding since William married Catherine Middleton in 2011 in a lavish ceremony at Westminster Abbey.

Harry's marriage to Markle will not be the first time a British royal has wed a divorcee. The British media has previously compared Markle to Wallis Simpson, the divorced American whose relationship with King Edward VIII led to his 1936 abdication.

However, there is significantly less controversy around this union given that in 2005, Prince Charles, the heir apparent to the throne and a divorcee himself, wed Camilla Parker-Bowles, who had also been married previously.