Prince William is to marry Kate Middleton next year after proposing to her using his mother's engagement ring.

The Prince revealed he gave his long-term girlfriend the distinctive blue sapphire ring that belonged to Diana, Princess of Wales, to make sure she "didn't miss out on the excitement".

Miss Middleton, showing off the ring alongside her husband-to-be, told reporters that joining the Royal Family was a "daunting prospect". But she added: "Hopefully I'll take it in my stride."

Prince William said of their engagement: "The timing is right now, we are both very, very happy."

Clarence House said in a statement: "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."

The Queen has been quick to give the pair her blessing, a Buckingham Palace spokeswoman said: "Both the Queen and the Duke of Edinburgh are absolutely delighted for them both."

David Cameron was amongst the first to congratulate the couple. The Prime Minister said he was "delighted" and sent the couple his very best.