Lauren Silverman flashed her huge £2.5 million diamond engagement ring after she left Britain's Got Talent auditions.
The socialite, 44, was spotted hand in hand with her husband-to-be Simon Cowell as she stepped out with the sparkler on her finger.
She looked sophisticated in a cream jacket which she layered over the top of a white high-necked crop top.
Lauren flashed a tiny slither of midriff and teamed her look with a pair of khaki trousers and gold chain.
She added a pair of nude heels and held a snakeskin handbag in her ring hand.
BGT judge Simon ditched his usual light blue jeans for some smart black trousers and a black long-sleeved top.
Simon's fellow judge David Walliams has been quick to joke with Simon about the engagement.
After a contestant incorporated an engagement into an audition, the children's author joked that it took Simon seven years to pop the question.
Jewellery buffs have calculated the cost of the ring and said that the diamond is incredibly valuable.
Alexandra Michell Gemologist Prestige Pawnbrokers of Channel 4 ’s Posh Pawn told MailOnline: "I would estimate this ring is a 15ct oval cut diamond, the stone is a colour D and internally flawless… the best grade on the market."
"I’d estimate the retail value at $3.4million or £2.5 million. This is very classic in style; a single stone on a white gold or platinum band, to really show off the star of the show- the diamond."
He asked Lauren to marry him during a luxurious trip to Barbados over the new year.
Eric and Lauren's other son Adam, 16, were both present at the proposal.
Simon had previously turned his nose up at the idea of marriage, saying he "didn't believe" in it.
But the dad-of-one quickly changed his tune after falling madly in love with Lauren.
A source told The Sun: "Lauren was absolutely stunned and never in a million years expected Simon to pop the question. She burst into tears - happy tears - and obviously said yes straight away."
"Lauren has been Simon’s rock over these past few years - supporting him when he broke his back, and through thick and thin generally. They make a wonderful couple.
"Whilst Simon never thought he was the marrying type, he’s realised he’s met the woman of his dreams - and couldn’t be happier. In the words of Beyoncé, it was time to put a ring on it."
A friend told People magazine: "They are both super happy. They've been together a long time now and adore each other so it's not a huge surprise to their close friends."
