The route was first climbed by Ryan Pasquill just a few weeks ago. Ryan is a superbly talented climber, operating at a high level in bouldering, trad climbing and sport climbing.
Ryan suggested a grade of E9 7a/b for Gerty Berwick, describing the highball crux as around Font 8A in difficulty.
You can read more about both Ryan's and James' ascents on the UKC news page:
In this clip, filmed by Hotaches, James is working the moves on the route, which was at the time, still a project. The clip was filmed around one year ago.
You can see more video footage of hard gritstone at the Hotaches Blog, including a clip of Ben Cossey headpointing Simba's Pride at Burbage.