In reply to Michael Hood:
Yes, moving up to and past the keyhole is the only awkward move (and even that's not very tough and has bomber protection, hence why the route has been downgraded from the original (Meirionydd) HVS 5b to a more sensible VS4c).
Several of the severes are nearer V Diff and it's often possible to move sideways along the waves between routes if one seems too hard! (There's a newish (2016) traverse detailed on the UKC logbook page at HS4a which I've been meaning to have a go at!)
Post edited at 19:36