When Michelle Williams retreated to her hotel room after a long day promoting her new movie, Oz: The Great And Powerful, in San Diego, all she could think about was sinking into her king-size bed. The last thing she expected was to find boyfriend Jason Segel and six-year-old daughter Matilda waiting expectantly, the room scattered with her favourite purple flowers.

“Matilda was sitting on the bed, clutching a lavender bouquet,” reveals a close friend of Michelle. “It wasn’t until Michelle picked her up to give her a kiss that she saw a little note tucked among the blooms that read, ‘Will you marry me?’” The friend says it was no secret that Jason, 32, wanted to marry Michelle, so it was impressive that he managed to spring the proposal on her.

“He flew in from New Jersey with Matilda on Michelle’s last day at Comic-Con,” says our source. “It was tough making it a surprise because he’s been telling her from day one that he was going to marry her.”

The proposal is exactly how Michelle, 31 – who’s finally found love after the sorrow of losing Matilda’s dad Heath Ledger to an accidental drug overdose in 2008 – wanted it. “There was no big fanfare – it was easy breezy, just like the two of them are,” the friend says. The same laid-back attitude applies to the ring – or lack thereof.

Read more about Michelle and Jason, plus see more celebrity engagements in this week's Woman’s Day on sale Monday July 23, 2012.