The happy couple announced their wedding plans on Tuesday (16Nov10), confirming they became engaged during a trip to Kenya last month (Oct10) and will tie the knot in London next spring or summer (11).
Within minutes of the announcement, Cameron passed on his congratulations to the young royal - and he later addressed the British public, promising the wedding day will be a "great day of national celebration".
Cameron says, "This is incredibly exciting news and I am sure that the whole country will want to pass their very best wishes to the happy couple and wish them an incredibly long and happy life together... It's a great day for our country, a great day for the royal family, and obviously a great day for William and Kate.
"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."
Middleton's father Michael adds, "We wish them every happiness for the future."
William and Kate have been a couple for eight years after meeting at St Andrews University in Scotland in 2002.