In reply to colin struthers:
> A friend and I climbed this route in Twll Mawr yesterday. After completing the crux move right on the first pitch and having moved back left to the groove/arĂȘte I then pulled on a large block - which I think moved.
The offending loose block has now been safely removed. It was big and definitely loose, it came off with just a couple of gentle pushes with my foot.
Luckily if anything it has improved the crux, it's no harder now, but the temptation to use holds on the groove for a rest after the crux is no longer an option.