Simon Cowell's Ex, Terri Seymour, Sits On His Lap As They Share Car Home After His Birthday Celebrations (PICTURES)

Errrrm, That's Not Lauren, Simon!

We have a feeling Simon Cowell will be in the doghouse with his baby mama Lauren Silverman when she sees these pics of his ex, Terri Seymour, sat on his lap in the back of a car after a night out. And judging by Si's reaction, he knows he will be too!

The pair - who previously dated for six years before splitting in 2008 - were snapped getting cosy in the back of a car after celebrating his 54th birthday with a meal at Sur in West Hollywood on Monday night.

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Simon Cowell and Terri Seymour

Simon - who to set to become a father in just a few months with Lauren - looked to be embarrassed as the TV presenter perched her behind on his knee, covering his face with his hands.

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Simon looked as if he knew he was in trouble as Terri sat on his knee

The pair had earlier been joined at dinner by Simon's former 'American Idol' co-judge Randy Jackson, along with a mystery blonde woman.

Simon later took to Twitter to thank fans for their birthday wishes, while also inviting Sinead O'Connor to come on 'The X Factor', after she slated the music mogul and his TV show for 'murdering music' in a recent interview.

"I think sinead o'connor would be a real fun guest judge on X factor. She loves the show and everything I do. Let me know sinead," he tweeted.

"And I had a great birthday yesterday. Thanks again for all of your tweets," he added.

Lauren Silverman: 9 Facts In 90 Seconds
Lauren Silverman: 9 Facts In 90 Seconds(01 of09)
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1. Nobody seems to know whether she's called Lauren or Laura. Or both. So let's get this one cleared up once and for all. It's definitely LAUREN. We think. (credit:Getty Images)
Lauren Silverman: 9 Facts In 90 Seconds(02 of09)
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2. She's 36. That's 17 years younger than Simon Cowell so yes, he is indeed *adopts nana voice* old enough to be her father, tsk tsk etc, etc. (credit:WENN)
Lauren Silverman: 9 Facts In 90 Seconds(03 of09)
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3. She is still technically married to one of Simon's bezzies, property developer Andrew Silverman. But according to Us magazine, the estranged couple have been 'unhappy for some time and a divorce is in the works'. Phew. (credit:Splash)
Lauren Silverman: 9 Facts In 90 Seconds(04 of09)
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4. She's been friends with Mr. Cowell for some time having holidayed with him in St Barts in August last year (along with with hubby Andrew). She also joined Sinitta and Si on holiday in 2011. (credit:Splash)
Lauren Silverman: 9 Facts In 90 Seconds(05 of09)
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5. She's a socialite. You know, like Paris Hilton. (credit:WENN)
Lauren Silverman: 9 Facts In 90 Seconds(06 of09)
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6. She's a dead ringer for Simon's ex fianceé, Mezhgan Hussainy - so much so that even we couldn't initially tell them apart when they all holidayed together last year. Can you? (Mezhgan's in the centre of this pic, Lauren's on the right) (credit:Splash)
Lauren Silverman: 9 Facts In 90 Seconds(07 of09)
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7. Just like Simon, she loves a ciggie, although we're hoping now she's preggers she's kicked the filthy habit. (credit:WENN)
Lauren Silverman: 9 Facts In 90 Seconds(08 of09)
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8. She pretty much knew all there was to know about Simon Cowell before allegedly rubbing belly buttons with him. We know this because she was at the launch party for his *coughs* unauthorised biography, 'Sweet Revenge: The Intimate Life of Simon Cowell' in April 2012. (credit:Getty Images)
Lauren Silverman: 9 Facts In 90 Seconds(09 of09)
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9. She's not to be confused with Laura Silverman (right) who is the actress sister of US comedian Sarah Silverman (left). (credit:Getty Images)