William asked her father for her hand
The Royal wedding will be in spring or summer
Kate Middleton and William will live in north Wales once married
Pair's first ever interview to be broadcast tonight
William is 'excited and thrilled', says Cameron
Prince William and Kate Middleton are engaged and will marry next year, Clarence House announced today.
William proposed during a holiday in Kenya last month after asking Kate's father for his daughter's hand.
The couple, who are both 28, have been together for a marathon eight years. Kate had been dubbed 'Waity Katy' amid criticism she was hanging on for a proposal but now her wait is finally over.
They will appear in public for photographs later today, when the Princess-in-waiting is expected to show off her engagement ring and the first ever interview with the pair is being broadcast tonight.
David Cameron said William is 'extremely excited' and 'thrilled' as he appeared outside No10 to welcome the news.
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Prince William and Kate Middleton at a wedding last month
Engaged at last: Prince William and Kate Middleton arrive together at a friend's wedding last month. It was significant because usually they arrive at events separately
Their wedding will be the biggest royal event since the wedding of Prince Charles and Diana in 1981.
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Clarence House said: 'The Prince of Wales is delighted to announce the engagement of Prince William to Miss Catherine Middleton.
'The wedding will take place in the Spring or Summer of 2011, in London. Further details about the wedding day will be announced in due course.
'Prince William and Miss Middleton became engaged in October during a private holiday in Kenya.
'Prince William has informed The Queen and other close members of his family. Prince William has also sought the permission of Miss Middleton's father.
'Following the marriage, the couple will live in North Wales, where Prince William will continue to serve with the Royal Air Force.'
A Buckingham Palace spokesman said: 'Both the Queen and the Duke of Edinburgh are absolutely delighted for them both.'
The couple at RAF Cranwell in 2008 when William received his wings
Young love: The couple at RAF Cranwell in 2008 when William received his wings
William and Kate at a Six Nations rugby match in 2007
At ease: William and Kate at a Six Nations rugby match in 2007
It is claimed personnel at Westminster Abbey have been contacted about arranging a royal wedding in the second week of August.
David Cameron and Labour leader Ed Miliband both said they were 'delighted' for the couple.
The Prime Minister was told of the engagement during the Cabinet meeting this morning and relayed it to ministers.
He emerged from No10 just before 1pm to express his joy at the announcement and revealed he had just spoken to the Prince.
'I spoke to Prince William a few moments ago and passed on my congratulations. He was obviously extremely excited about the news and thrilled about what lies in store. It was wonderful to have that word with him and pass on my best wishes,' he said.
Mr Cameron added: 'This is incredibly exciting news and I am sure the whole country will want to pass on their congratulations.'
Recounting how he was told during the Cabinet meeting, he said: 'There was a great cheer that went up and a banging on the table. This is a great moment of national celebration but this is two young people who love each other who have made this decision and we must give them space.'
He said: 'It's great to have a piece of unadulterated good news that everyone can celebrate and be happy for them. I am sure it will be something when the country will come together. I remember when William's mother got married, I slept on the Mall that night.'
Earlier this month, the Daily Mail exclusively revealed Kate Middleton's parents were guests at a private shooting party on the Queen's Scottish estate.
The move was seen as highly symbolic and an indication that the middle-class Middleton family were now firmly being welcomed into the royal fold.
It is now clear that Kate and William were already engaged at the time of the visit to Birkhall, Prince Charles' private residence on the Balmoral estate.
The invitation to Mr Middleton, a former airline despatcher, and ex-air hostess Carole shows the Royal Family were keen to start off on the right foot as Kate moves to becoming a princess.
William and Kate after a party at Mahiki
Out on the town: William and Kate after a party at Mahiki in 2006
The Prince and Kate at a rugby sevens event
Early days: The Prince and Kate at a rugby sevens event in 2003
She and William first met at St Andrews University where they were both studying history of art and lived close to each other in the halls of residence.
It was at a charity fashion show in March 2002, when Kate modelled a sheer black lace dress, that she was said to have first turned the Prince's head.
They moved in together with friends in 2002 but are not thought to have become a proper item until around Christmas 2003.
Their romance was exposed on a skiing holiday in Klosters in 2004 but William famously proclaimed: 'I don't want to get married until I'm at least 28 or maybe 30.'
They split up in April 2007 as William became increasingly involved in his career in the Armed Forces but were secretly united within weeks.
In the past few months, the pair have been 'road-testing' married life on Anglesey, in Wales - although officially Kate was still living at her parents.
There was a significant change last month when they were seen together in public at a friend's wedding.
They notably walked in to the ceremony in Gloucestershire on October 23 together, with Kate beaming.
Usually, they always arrived at events separately to avoid being pictured together.
The last time Kate was seen was in July and it is thought she had been kept in the background ahead of the engagement announcement.