Watch this woman explode with joy when a man dressed in a dinosaur outfit proposes to her

• Chris Jones proposed to his girlfriend, Katie Parker, in the middle of the London Marathon on Sunday.
• He was wearing a dinosaur costume.
• A video of Parker joyously freaking out went viral.
• Jones said he ran the marathon in a dinosaur costume to raise money for the children's hospital that treated his cousin who was infected with a rare and deadly flesh-eating virus.
  

At Sunday's London Marathon, Chris Jones ran all 26.2 miles while wearing a Tyrannosaurus Rex costume.

But halfway through, he zipped off his dinosaur costume and proposed to his girlfriend, Katie Parker.

"I've been planning for about a year now," Jones told INSIDER. "She was surprised. She had no idea."

Jones ran the marathon in costume to raise money for the Evelina Children's Hospital, which treated his cousin James when he was infected and nearly killed by a rare, flesh-eating virus when he was 20 months old.

After two months of constant treatment in the hospital, James was finally cured. Now, about six years later, Jones said the apparent under-funding of the National Health Service in the UK, which pays for treatment like what Jones received, inspired him to raise money for the hospital.

"It was like a really rare strain at the time," Jones said. "They had to research and develop whilst they were treating him. They probably operated him maybe 20 or 30 times to basically repair his upper arm."

Jones ran the marathon with Parker's father, Phil Parker, who carried the ring and was dressed as a "Jurassic Park" ranger. The two arranged for a group of around 20 friends and family members to be at a "cheer point" on Tower Bridge, around halfway through the marathon's course.

"It was very emotional. She cried. I cried. Her dad cried. Everyone cried," Jones said. "Everyone was just in shock."

A BBC reporter interviewed the couple after the proposal. Parker's overjoyed reaction went viral.

Later on, Jones posted the full proposal video on Twitter.

But after the proposal, Jones had to go. He had 14 miles left in the marathon.

"I had to go run the second half of the race," Jones said. "She was like, 'Oh, he's gone now?'"

Jones finished the marathon in about six hours — still wearing the T-Rex costume.

Afterward, he and Parker attended a party thrown by the Evelina Children's Hospital charity. He raised nearly $3,700.

James is seven now. Jones says he's doing well.

"He's about the most active, sporty little child you can find," Jones said. "He runs around, winning football trophies. At the time, we all thought it was definitely life-threatening, and the hospital did just such a great job of getting him back into health."

As for the T-Rex costume, he said we haven't seen the last of it.

"I won't be walking down the aisle with it," Jones said. "But I might make a speech with it."

Join the conversation about this story »

NOW WATCH: Why Apple makes it so hard to get a new iPhone battery