LONDON (AP) — The London Marathon started five days ago, and Tom Harrison is nearly done.

It's not that he's a slow runner. It's that he's a slow crawler, particularly wearing his gorilla suit.

The man dubbed Mr. Gorilla is raising money for the Gorilla Organization — so far more than 22,000 pounds ($28,500) have been pledged.

He's hopeful of finishing the race Saturday, with his two sons expected at the finish line to celebrate his feat.

He ran the marathon last year raising money for gorillas, but is finding crawling much more stressful.

"It's shoulders, hamstrings, glutes, quads, from the constant crouching," he says. "We're not really designed to do that."

Harrison says the money will be used to protect endangered gorillas in Africa.