Holly Brafman's visit to the festival was carefully planned by her boyfriend Ashley Hill, whose attention to detail was so painstaking he booked time off work for her without her knowing.

Her weekend in the county included a flight in a hot air balloon and, as it rose into the sky, she saw a 20 metre banner laid out on the ground by Ashley, asking her the question: "Will you marry me?" Mr Hill, a 28-year-old quantity surveyor from London, had been planning the stunt since June and said he was so nervous when the banner finally came out that he could not stop shaking.

He said: "We went up in the evening and all day I was just worrying it might start raining or something.

"When the banner went out I thought she would say yes, but there was a part that worried she might say no."

Miss Brafman, a 26-year-old PR consultant, said she had been completely surprised by the proposal and added she had not stopped smiling since.

She said: "I was over the moon when it happened. I was so shocked and the whole thing was just amazing.

"The crew on the day were amazing too, they managed to keep the whole thing to themselves all day and when we got to the bottom they gave us a bottle of champagne."

A spokesman for Northampton Borough Council, which organised the balloon festival, said: "All the pilots and crews as well as the organisers of the balloon festival wish them a marriage made in heaven, or least up in the clouds!"