Kate Middleton will wear Diana's enagement ring

(AP)

Prince William has given Kate Middleton his mother's engagement ring, it emerged tonight.

The Prince proposed with the blue sapphire and diamond ring that his father, the Prince of Wales, gave to Diana, Princess of Wales, in February 1981.

He said today: "As you may have recognised, it's my mother's engagement ring, so of course it's very special to me and Kate's very special to me now as well, and it's only right the two are put together.

"It was my way of making sure my mother didn't miss out on today, and the excitement and the fact that we're going to spend the rest of our lives together."

Diana chose the ring, which cost £28,000 at the time, from a selection presented to her by jewellers Garrard.