LONDON, England (CNN) -- Britain's Prince Charles has announced he will marry his longtime lover, Camilla Parker Bowles, the woman partly blamed by Princess Diana for the breakdown of her marriage to the heir to the throne.
The wedding will be a civil ceremony in Windsor Castle on April 8, followed by a service of prayer and dedication in St. George's Chapel at which the Archbishop of Canterbury will preside.
Charles said he and his wife-to-be were "absolutely delighted" at their engagement.
When offered congratulations as he entered Goldsmiths' Hall in London for an engagement Thursday morning, he said: "Thank you very much, you're so kind." He added: "I am very excited."
On their marriage, Parker Bowles will be given the title of Her Royal Highness the Duchess of Cornwall.
When Charles becomes king, Camilla will not be known as Queen Camilla but as the Princess Consort, according to Charles' office.
A statement on behalf of Queen Elizabeth II said: "The Duke of Edinburgh and I are very happy that the Prince of Wales and Mrs. Parker Bowles are to marry. We have given them our warmest good wishes for their future together."
Charles and Diana's two sons William and Harry said they were "delighted" at the announcement, a Clarence House aide told the UK's Press Association.
The princes want the couple to be happy, the senior official added.
British Prime Minister Tony Blair, who in 1997 mourned the death of the "People's Princess" Diana, said he was "delighted for the Prince of Wales and Camilla Parker Bowles, it's very happy news."
He said the Cabinet had sent congratulations and good wishes, adding: "We all wish them every happiness for their future together."
The announcement, four days before St. Valentine's Day, came as a surprise to many royal observers.
Charles' love life has been the cause of much speculation in Britain since the death of Diana in a Paris car crash, one year after the couple divorced.
Parker Bowles, 57, who divorced her husband Andrew in 1995, has been the significant love of Charles' life in recent years but has always faced an uphill struggle to rival his former wife in the public's affection.
Since then, and after several years of carefully choreographed appearances together, Parker Bowles has now been widely accepted as Charles' long-term partner.
She openly shares official rooms with the prince, 56, at his Clarence House residence in London.
On the death of the queen, Charles would become the titular head of the Church of England, and some Anglicans remain opposed to the remarriage of divorcees.
On Thursday Archbishop of Canterbury Rowan Williams, who heads the world's Anglicans, said he was pleased the couple had decided to take "this important step."
"I hope and pray that it will prove a source of comfort and strength to them and to those who are closest to them."
Parker Bowles will be stepmother to William and Prince Harry, second and third in line to the British throne, respectively.
Diana partly blamed her husband's relationship with Parker Bowles for the failure of her marriage. "There were three of us in this marriage, so it was a bit crowded," Diana said in a 1995 TV interview.
In 1994, Charles admitted in a TV documentary that he had strayed from his marriage vows, but insisted the infidelity happened only after the marriage was "irretrievably broken down, us both having tried."
It was widely assumed, but never confirmed, that Parker Bowles -- who has two children, Tom 30, and Laura, 24 -- was the other woman.
Hurdle
CNN's Richard Quest said the 2002 death of the Queen Mother, Charles' grandmother, had apparently removed the major hurdle to his marriage to Parker Bowles.
Friends of the prince welcomed news of his impending marriage. Conservative MP Nicholas Soames said he was "absolutely delighted."
"I'm very, very happy for both the Prince of Wales and Mrs. Parker Bowles. I think it's wonderful," he told PA.
A spokeswoman for Princess Diana's brother Earl Spencer told PA he would be making no comment on the announcement.
Diana's biographer, Lady Colin Campbell, said Camilla was a marked contrast to Diana, preferring simple country pursuits to a life of Hollywood-style glamor.
She said she expected a much simpler wedding to the major spectacle of Charles' wedding to Diana in London's St. Paul's Cathedral in July 1981.
Campbell said Charles' office Clarence House had mounted a long-running campaign to make marriage between the couple acceptable to the British people.
An opinion poll in June last year showed Britons would narrowly approve of a marriage between Charles and his partner.
A second marriage for the Prince of Wales would have the support of 32 percent of the British public, with 29 percent opposed, according to the Populus poll conducted for The Times newspaper.
However, it was revealed that most Britons -- 38 percent -- did not care whether Charles and Parker Bowles married.
'Journey'
Three years ago Prince Charles answered a question about whether he planned to marry Parker Bowles by saying, "You can't be certain about anything."
On an interview given to the UK tabloid Daily Mail to mark the 25th anniversary of The Prince's Trust, Prince Charles was asked whether he planned to remarry. He said: "Will I be alive tomorrow? Who knows what the Good Lord has planned. You can't be certain about anything. I don't know.
"I just think it's important, particularly as I get older, to think about the journey that's coming next."
Thursday's wedding announcement comes before the completion of the inquest into Diana's death.
Former head of the Metropolitan Police Sir John Stevens is still investigating the car crash in which she died in August 1997.
Charles' biographer, Penny Junor, told Reuters: "This will divide opinion and some people will think it is the end of the world. But once it has happened, people will accept it.
"He's very much in love with her and she with him. That's just the way it is."
When Charles becomes king, Camilla will not be known as Queen Camilla but as the Princess Consort, according to Charles' office.
some people before said that if Charles married he wouldnt be able to be king, i said this wasnt true ... but look ... he can, but Camilla cant be queen ... to all those who doubted the power of ME
I think it's since the Church changed the laws about divorcees being allowed to remarry that he's allowed to still be King.
There was a poll done in the UK after the announcement that said that 70% of the population didn't like the idea of them marrying. She is never going to be properly accepted by the British people, she will always be the "other woman" who ruined Charles' and Diana's relationship.
I could not give a damn reallly, I think we should get rid of the royal family. All I care about is one thing and that is how much is this wedding going to cost as no doubt we will probbaly be footing the bill in some form.
Prince Charles' bride-to-be holds up the symbol of her new status for all the world to see
Appearing together at a Windsor Castle reception the couple were clearly thrilled that the issue of their relationship, which has been in limbo for many years, is finally resolved
As Charles' wife Camilla will become the Duchess of Cornwall. She will be only the third woman in history to hold the title. The first was Caroline of Ansbach, in 1714, and the other was Mary of Teck (above) who received it when her husband's father, Edward VII, ascended the throne in 1901
Camilla Shows Off Her Enagagement Ring
Newly engaged Camilla Parker Bowles was glowing as she showed off her dazzling engagement ring – a royal family heirloom – at a Windsor Castle reception on Thursday evening. The platinum-set jewel features a square-cut central diamond flanked by a further three baguette-cut stones.
Appearing for the first time in public as the Prince of Wales' intended, the 57-year-old divorcee revealed that Prince Charles went down on bended knee to ask for her hand. The couple are due to tie the knot in a civil ceremony followed by a blessing at St George's Chapel in Windsor Palace on April 8.
According to reports the announcement of the engagement was planned for Valentine's Day, but had to be brought forward after the news was leaked to a British newspaper.
At the reception Camilla, who wore a full-length fuchsia gown by Jean Muir for her first appearance as a bride-to-be, admitted: "I am only just coming down to earth". Her Prince, wreathed in smiles, was similarly enthusiastic and announced, "I'm very happy".
Camilla's marriage will make her the second highest-ranking women in the kingdom after the Queen. Upon her nuptials she will be known as Her Royal Highness, and will take precedence over both Princess Anne and Prince Edward's wife Sophie.
As Prince Charles' wife, she will become Duchess of Cornwall, only one of three women in British history to hold the title. The two previous Duchesses – Caroline of Ansbach and Mary of Teck – held the title only briefly before becoming Princesses of Wales, a title which Camilla will not hold.
When Charles inherits the throne Camilla will be known as the Princess Consort, although there is apparently sufficient leeway in the current arrangement to allow Camilla to become Queen should the public support such a move.
It sounds funny, but I thought her ring would be bigger and better than that. I think J-Lo and Ben Affleck's engagement ring was better than that and they were super-crass about everything, you would think a Prince's engagement ring woudl outdo a movie star's ring.