Prince William and Kate take on Prince and Princess of Wales titles, King Charles III confirms in first speech

Prince William and Kate's new titles have been confirmed by King Charles III in his first speech as monarch on Friday (Saturday morning AEST).

His Majesty confirmed his eldest son, now the heir-apparent, would take on his former title as Prince of Wales and the Duchess of Cambridge would take on Princess Diana's former title.

"As my heir, William now assumes the Scottish titles which have meant so much to me," Charles began.

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"He succeeds me as Duke of Cornwall and takes on the responsibilities for the Duchy of Cornwall which I have undertaken for more than five decades.

"Today, I am proud to create him Prince of Wales, Tywysog Cymru, the country whose title I have been so greatly privileged to bear during so much of my life and duty.

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"With Catherine beside him, our new Prince and Princess of Wales will, I know, continue to inspire and lead our national conversations, helping to bring them marginal to the centre ground where vital help can be given."

The Duke and Duchess of Cambridge — titles given to them by the Queen on their wedding day — now have taken on the additional titles of Duke and Duchess of Cornwall and will also inherit the Scottish titles of the Duke and Duchess of Rothesay.

As heir to the throne, Prince William also inherits the Scottish titles of Earl of Carrick, Baron of Renfrew, Lord of the Isles, as well as Prince and Great Steward of Scotland.

The couple adjusted their social media titles just hours after the Queen's death on Thursday (Friday morning AEST) to reflect the additional duchy of Cornwall but moments after the King's speech, their titles were updated again.

The newer titles mean Kate takes over from Princess Diana, given Camilla never adopted the Princess of Wales title out of respect to the late royal.

"[Kate] appreciates the history associated with this role but will understandably want to look to the future as she creates her own path," royal commentator Omid Scobe said, quoting a source, in a tweet.

Royal commentator and author Katie Nicholl recently told 9Honey the Duchess of Cambridge's success in her royal role had come down to the fact she hadn't tried to be the next People's Princess.

"I think one of the great strengths of Kate, and one of her real successes, is that she hasn't followed in Diana's footsteps," Nicholl said.

"I don't think she seeks to emulate Diana. I think she was so aware of the comparison right from the outset, but despite the weight of that engagement ring on her finger, and the significance that that holds and the comparisons it inevitably draws, she is actually a very different woman.

"Her success has been in carving her own identity in the royal family as the Duchess of Cambridge and making that role herself."