KATE MIDDLETON secretly collapsed just hours before her first public appearance  since announcing her pregnancy!

But royal insiders told The ENQUIRER that the Duchess of Cambridge was determined to attend the event despite a crippling new bout of morning sick­ness.

“KATE COLLAPSED IN A CHAIR while she was getting ready for the evening,” said an insider.

“She was in so much distress that she could barely stand up. But she took a page out of the late Princess Diana’s playbook and soldiered on because she shares Di’s strong sense of duty.

“Kate would never do anything to endanger her baby, but when she says she’s going to do something, it’s important to her to carry it through.”

The 30-year-old beauty glowed in a dark green floor-length Alexander McQueen gown as she presented trophies and posed for pictures at the BBC Sports Personality of the Year awards in London on Dec. 16.

It was the duchess’ first public event since she was hospitalized for three nights with acute morning sickness after revealing that she’s expecting her first child with Prince William. The cou­rageous royal was rushed back to Kensington Palace after only 45 minutes to continue her re­cuperation.

“It was particularly tough for Kate because William was in Wales working a shift for the Royal Air Force,” said the in­sider.

“He didn’t want her to go, but Kate insisted she’d be fine on her own. William knows that once Kate sets her mind to do something, nothing will stop her. He definitely sees a lot of his mother in her.”

Diana was just 20 when she became pregnant with William and often struggled through her royal duties while battling nausea.

“She (Diana) had terrible morning sickness and she said the royal family never heard it,” Ingrid Seward of Britain’s “Majesty” magazine said on Good Morning Ameri­ca.

“She was doing her duty and feeling absolutely ghastly. So once again Diana is there, paving the way for Kate.”