Olivia Wilde instantly knew Jason Sudeikis was 'The One'.

The actress told USMagazine.com that she knew she wanted to marry him as soon as they met, saying: "Oh, how could I not know?"

However she said she has no idea when they will tie the knot, saying: "I still have no clue."

The pair began dating in November 2011 and moved in together last year, with the brunette beauty admitting she fell "blissfully, hopelessly, wildly in love."

Rumours first began swirling that the couple were secretly engaged in early December.

A source previously said: "Everyone in town is buzzing about the wedding. They have already booked the venue and are in the process of finalizing the rest of the details.

"Jason is a hometown boy at heart, and he is super close to his family and all his friends there. It has always been his dream to get married back in Kansas City."

Olivia split from her first husband eight years, Tao Ruspoli, in February 2011 and had a few brief flings before settling down with Jason.

After a few months of dating, things got serious and she recently put her $2.5 million Los Angeles home on the market so that she could move in with Jason in New York City, where his show is filmed.

A source said: "Olivia is so over commuting back and forth between LA and New York. At first she was worried that if she left the West Coast the acting offers would dry up. But these days she is more focused on her relationship than her career. She's all about what's best for them as a couple and that means living in NYC."