Ben McCreadie, 28, pulled up on the 26th mile to get down on one knee in front of stunned Laura Rendell, who cheered him on in the crowd.
And the hospital worker refused to finish the London race until 30-year-old Laura agreed to marry him.
Luckily she said “yes”, and Ben put an engagement ring on her finger before running off to complete the epic race.
Ben said: “I couldn’t think of a better way to do it. She didn’t have a clue.