Mike Dagenais' plans for a very public Valentine's Day proposal have paid off in a big way.

He got down on one knee Thursday at noon and asked for his girlfriend's hand in marriage, next to a huge billboard displaying a photograph of her face.

She said, "Yes."

Dagenais had been trying to keep the giant billboard a secret from his girlfriend all week so he could stage the perfect surprise proposal.

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Edmonton man uses a billboard to propose to his valentine. 1:16

Mike Dagenais' plan for a Valentine's Day wedding proposal may be the best worst-kept secret in the city.

Dagenais, 55, is proposing to his girlfriend of three years by displaying her face across a central Edmonton billboard.

The digital sign at Kingsway and 119th Street proclaims "Laurie M., I adore you. You're my best friend. And my true soulmate. Will you marry me?"

The billboard prompted some calls from media since going up on Monday, with Dagenais doing some on-air interviews for TV and radio.

Even so, Dagenais said his girlfriend may be the last one to learn of his highly-public gesture.

'Trying to play it cool'

"She usually only listens to podcasts in the car so she didn't hear anything on the radio and she doesn't have a TV so she never saw anything on TV. She has no idea," Dagenais said.

"Thankfully no one has said anything because I'm supposed to show up at her work tomorrow, take her to the billboard, and propose then."

While Dagenais didn't want to share Laurie's full name, he said she is a natural beauty, awesome mom and all around Superwoman.

"She knows something's up and I'm trying to play it cool."

Mike Dagenais is proposing to his girlfriend of three years by displaying her face across a central Edmonton billboard. (Dave Bajer/CBC)

The link to Dagenais' photography website on the billboard led some on social media to hypothesize the sign was a promotional stunt.

Dagenais said he has started a photography business to keep him busy when his seasonal work as an oil and gas inspector slows down, but the proposal is real.

"It really is all about Laurie," he said.

"If I get some extra work out of it, then that's great, but I'm just trying to showcase this beautiful lovely woman and propose to her in a different way and we'll see what happens."

I hope she gets blown away. -Mike Dagenais

He's been plotting the proposal for more than a year. He has a diamond ring and plans to get down on one knee dressed in full suit and tie, an ensemble he has only ever worn once before in his life.

He said his girlfriend's family and co-workers have been sworn to secrecy and he's been in cahoots with her boss.

Dagenais initially planned to propose on Tuesday but Laurie was laid-up with a bad migraine. In the meantime, keeping his plans under wraps has become increasingly difficult.

He hopes his cover hasn't been blown.

"I'm just splitting a gut over this," he said. "She did send me a text that her coworkers are acting unusual towards her.

"It seems like a lot people know, but Laurie thankfully does not know yet and I don't want to say anything until tomorrow if I can get through today."

In the meantime, he will be wringing his hands, hoping for a "Yes."

"She doesn't like a lot of attention and neither do I, but I've had to suck it up these last few days so she can have a nice surprise and I hope it is a surprise.

"I hope she gets blown away."