will bosi raven tor mutation climbing
Bosi on "Mutation" in 2018; (photo/Hot Aches Productions)

First Repeat: Bosi Conquers McClure’s ‘Mutation’ 23 Years Later, Upgrades to 5.15a

Twenty-three years after Steve McClure’s first ascent, ‘Mutation’ at Raven Tor finally sees its first repeat.

Cut to 1998, the height of British climbing superhero Steve McClure’s power. The camera rolls at Sheffield’s Raven Tor as the trippy Europop cues up.

McClure’s partner, Rupert Davies, yards up to the first hold on “Evolution,” 8c+ (5.14c), a sloppy, slopey sidepull with minimal actual surface. He paws at it and exclaims, “Oh, that is rubbish!”

Minutes later, McClure nails the first ascent of the climb’s punishing extension. The route, aptly called “Mutation” and graded 9a (5.14d), wouldn’t see another ascent until 2021.

After 4 years of prospecting at Raven Tor and over 40 days of concentrated effort, 22-year-old William Bosi finally ticked the first repeat on Halloween.

It was the Scotsman’s most extended project and among his hardest. If his 9a+ (5.15a) upgrade stands, it will be his third of the grade.


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He explained his rationale to Planet Mountain in language that’s easier to read than to decipher. Paraphrased, Bosi interprets the route as two distinct 8c+ climbs on top of each other. Linking the two, he reasons, makes the finished product harder than 9a.

He should know — he estimates he’s now finished “Evolution” 100 times. Would he go so far as to call “Mutation” the world’s first 9b? If so, it would predate Dani Andrada’s “Ali Hulk Extension Sit Start” by nearly a decade. Bosi broached the issue but erred on the side of caution.

“So ‘Mutation’ is the first 9b in the world? Perhaps, time will tell with other repetitions, but I think for now I will opt for the 9a+,” Bosi said.

Watching the sinewy McClure execute the moves in “Psyche” makes either seem equally likely. To watch him thrutch and contort his 5’6″ frame up the blue-streaked Raven Tor limestone is poetic and painful by turns. He celebrated Bosi’s repeat.

“My first reaction when I received the news was ‘Fantastic!’,” McClure said. “I was so happy for Will that he had finally done ‘Mutation.’ A few years ago, I was really worried that the route would get dirty and not see a repetition, so it was great when Will started working on it.”

Sam Anderson

Sam Anderson is a staff writer at GearJunkie, and several other All Gear websites.

He has been writing about climbing, cycling, running, wildlife, outdoor policy, the outdoor industry, vehicles, and more for 2 years. Prior to GearJunkie, he owned and operated his own business before freelancing at GearHungry. Based in Austin, Texas, Anderson loves to climb, boulder, road bike, trail run, and frequent local watering holes (of both varieties).