Ross Chilcott, 29, rappelled down the side of a building in the Markey Square area of Cambridge, England, tussled with a group of actors portraying the parts of criminals and took a diamond ring from one of the faux-crooks before dropping to one knee at the feet of his girlfriend, Amber Clarke, 28, cambridge-news.co.uk reported Monday.
"I'm so surprised. I had no idea at all. I can't believe it," Clarke said.
Clarke was lured to the right area by friend Hayley Woodroffe, 27, who was in on Chilcott's plot.
"I thought it was amazing, especially since she had no idea. When we were walking up to the Guildhall she actually said, 'This is something that Ross would do,'" Woodroffe said.
Chilcott said he got permission for the stunt from Cambridge City Council six weeks ago.
"I just knew she would say yes," he said. "I wanted to do it on her birthday, which was June 5, but I couldn't find the right venue. She loves seeing me embarrassing myself and she likes Batman so I knew she'd love it."