Cassandra Thorburn responds to news that her ex-husband Karl Stefanovic is engaged.

Karl Stefanovic’s ex-wife has responded to news of his engagement in a brief and no-nonsense statement, re-affirming her desire to make sure her children are happy and safe.

“I am just focused on helping those affected by the ever-changing landscape of my ex-husband’s life, to navigate it,” Thorburn told Fairfax Media on Saturday.

“His engagement doesn’t register with me on any other level.”

Stefanovic and Thorburn were married for 21 years and have three children, Jackson, 18, Ava, 12, and River, 10.

Thorburn’s comments come after Stefanovic and Yarbrough made their first public appearance as soon-to-be husband and wife at a Sydney event on Tuesday night.

Attending Harper's Bazaar Australia's 20th anniversary edition party at Barangaroo, the 43-year-old television presenter and the 34-year-old shoe designer appeared together, with one large, shining diamond ring between them.

It was confirmation after weeks of speculation and Yarbrough, a former model, was photographed on arrival flashing the ring.

Stefanovic and Yarbrough first met in December 2016, several months after The Today Show co-host separated from Thorburn. He and Thorburn finalised their divorce in October last year.

LISTEN: The Mamamia Out Loud team discuss Karl and Cass' public behaviour during their split. Post continues. 

Rumours of Stefanovic and Yarbrough's engagement have been circulating since they returned from a five-star holiday at a private Fijian island in late January, New Idea reports.

The talk intensified when Stefanovic posted a "Happy birthday" message to mark Yarbrough's birthday on Instagram last week - the picture showed the 34-year-old designer holding a glass of champagne, the shimmer of a diamond ring visible through the bubbles.

Yarbrough added to the speculation over the weekend by documenting her birthday celebrations on social media, her ring always ever-so-slightly in shot.

Now, finally, the engagement is confirmed and wedding planning will no doubt begin in earnest.