The Duke and Duchess of Cambridge have expressed their delight at the news of Prince Harry and Meghan Markle's engagement.
William and Kate said it had been "wonderful getting to know Meghan" since the American actress began dating Harry around 18 months ago.
A date for the wedding has been set for next spring, when the country will come together in scenes echoing Kate and Wills' own wedding in 2011.
In a joint statement released by Kensington Palace, William and Kate said: "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."
The Duke and Duchess of Cambridge said of the engagement: '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.'
— The Duke and Duchess of Cambridge (@KensingtonRoyal) November 27, 2017
Initially at least, the newly-engaged couple will move in together at Nottingham Cottage, where William, Kate, Prince George and Princess Charlotte will be their neighbours at Kensington Palace.
Harry and Meghan revealed they were an item a year ago after a six-month secret relationship, got engaged earlier this month in London and will marry in spring 2018.
The 36-year-old actress, who is best known for her role as Rachel Zane in US legal drama Suits, is believed to have charmed the Royal when he visited Toronto in the summer of 2016.
They managed to keep their relationship secret from the world - but it later emerged she had met William and Kate and he had met her family in California.
William was said to be deeply unhappy over his younger brother's decision to issue an unprecedented public statement, in which he lashed out at media intrusion and the "sexism and racism of social media trolls".
A lengthy and strongly-worded statement issued by Kensington Palace said there had been a "line crossed" in the abuse and harassment she has faced and it was "not right" that his girlfriend "should be subjected to such a storm".
It came after Meghan flew to London during a gap in her filming schedule and was photographed buying food on Kensington High Street, Princess Diana's favourite shopping street.
WHAT WILL MEGHAN'S NEW TITLE BE?
Meghan, who is divorced, could become a princess or alternatively be given the title Duchess of Sussex when she marries the fifth in line to the throne and joins the royal family.
But they are likely to wait until Prince William and Kate have their third child, which is due in April.
Bookmakers refused to take any more bets on the couple getting engaged last week as Meghan landed in London and started moving her belongings and two dogs to the UK.
Social media went into meltdown but they have had to wait until today to hear that the fifth-in-line to the throne has proposed to his actress girlfriend.
A Kensington Palace spokesman tweeted today: "The Prince of Wales has announced the engagement of Prince Harry and Ms Meghan Markle.
"Prince Harry and Ms Markle became engaged in London earlier this month. Prince Harry has informed The Queen and other close members of The Royal Family.
"Prince Harry has also sought and received the blessing of Ms Markle's parents. The couple will live in Nottingham Cottage at Kensington Palace.
"The wedding will take place in spring 2018. Further details will be announced in due course."
It is likely that the couple will, like Kate and William, be awarded a dukedom by the Monarch on the occasion of their wedding, with Vogue reporting that the newlyweds will become the Duke and Duchess of Sussex.
Under the British Monarchy, the title is only given to those who are born into royalty, meaning that if Meghan and Harry were to have children they would be referred to as princes and princesses.
The same went for Kate and William at their wedding six years ago with Wills adding Duke to his own title after the Queen granted the couple with a "dukedom".
Kate is only bestowed the royal title in reference to her husband known as Princess William, and once he inherits his father's title she can then be referred to as Princess of Wales.
The same goes for Meghan and Harry. The 36-year-old US actress may be referred to as HRH Princess Henry.
DOES MARRYING A ROYAL PUT MEGHAN IN LINE FOR THE THRONE?
Prince Harry is currently fifth in line to the throne and will move down to sixth when the Duke and Duchess of Cambridge welcome their third baby, expected to arrive in April.
However, while marrying Harry will give Meghan a royal title she will not join the line of succession.
Marriage to a royal does not put you in line to the throne and you are in only if you have succession rights in your own right.
Harry also asked Meghan's parents Thomas Markle and Doria Ragland, who divorced when their daughter was six, for her hand in marriage before popping the question a few weeks ago, it emerged today.
They said: "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 parent"'.
Harry, 33, and his American fiancee, 36, have not said where they will hold the ceremony but if they choose the UK most senior royals marry at Westminster Abbey, St Paul's Cathedral or the chapel at Windsor Castle.
'Prince Harry has also sought and received the blessing of Ms Markle's parents.
"The couple will live in Nottingham Cottage at Kensington Palace."
Just a week after the Queen celebrated her own 70th wedding anniversary, she and Prince Philip said in a statement: "delighted for the couple and wish them every happiness".
Prime Minister Theresa May offered her "very warmest congratulations", wishing the couple "great happiness for the future".
"I would like to offer my very warmest congratulations to HRH Prince Harry and Meghan Markle upon their engagement," said Mrs May in a statement.
"This is a time of huge celebration and excitement for two people in love and, on behalf of myself, the Government and the country, I wish them great happiness for the future."
Mrs May's predecessor David Cameron called the announcement "wonderful news", and wished the pair "a long and happy life together".
Justin Welby, the Archbishop of Canterbury, said he was "absolutely delighted to hear the news', wishing them 'many years of love, happiness and fulfilment".