“On Saturday afternoon, Simon was in the courtyard of his Malibu home with Eric and Adam, and he wanted to show them his new electric bike,” said the “America’s Got Talent” star’s former longtime flame, Terri Seymour, to the TV show “Extra,” where she is a correspondent.

“It’s very fast and very powerful,” Seymour said of Cowell’s new ride, which cost more than $20,000 — and has been banned from open roads in the UK because of the up to 60-mph speeds it can reach.

“I don’t think he realized how powerful it was, and he flew off the bike, landed on his back,” Seymour said.

Cowell is now recuperating after six hours of surgery Saturday night — and “actually just took a few steps,” Seymour said.

She said Cowell’s 6-year-old son Eric with girlfriend Lauren Silverman, as well as Silverman’s 14-year-old son Adam, were with him outside the family’s Malibu, Calif., home when he fell.

The star tweeted Sunday night, “Some good advice… If you buy an electric trail bike, read the manual before you ride it for the first time.

“I have broken part of my back. Thank you to everyone for your kind messages.”

Cowell “obviously was in a lot of pain, in agony” after the fall, Seymour said.

She said he was rushed to the hospital by ambulance and got an X-ray, which showed “immediately he needed surgery.

The break ”was 1 centimeter away from from his spinal cord, that is true,” she said — confirming reports from pals that he was lucky he wasn’t paralyzed.

“It’s bad, and he is in agony. [But] it could have been so much so much worse,” Seymour said.

She added that she talked to Silverman on Monday and that Cowell’s girlfriend told her he is already back to his famously bossy, driven self.

“He’s on his iPad, making phone calls, working,” Seymour said.

“She just told me he’s already bossing her around,” the TV entertainment reporter said, referring to Silverman.

Still, “He is going to need a lot of physical therapy,” Seymour said of Cowell.

She added that while he won’t be back for “AGT” to resume live Tuesday night, but otherwise, “You never rule anything out with Simon.

“Recovery is going to be a long road ahead. He’s so determined. He’s so upset to miss these live shows. It’s his baby — of course he wants to be there. Let’s just wait and see.”