When the Red Hot Chili Peppers headlined the humongous Reading Festival in England over the weekend, they closed their set with “By the Way.” The Reading Festival is the world’s oldest music fest still in existence and pretty much everybody’s grandmother and dog has played there.

But it was the Chili Peppers’ bassist, Flea, that caught our ear at this years show when he spoke about his meeting with Koko, the sign-language Gorilla. Koko was born at the SF Zoo in 1971 and understands more than 1,000 signs and 2,000 words of spoken English.

Flea described the encounter as “deeply emotional.” Watch the video.

PHOTO: Leon Wilson