In reply to Frank the Husky:
When I did this the other day it did wobble disturbingly so I decided not to stick a cam in the inviting slot behind it (actually I stuck it in but then took it out afterwards) but it didn't feel like it was going to part company with the cliff in the immediate future?
That said if someone experienced with trundling does knock it off it wouldn't really affect the route at that point as I think the difficulties are pretty much over! It might hit a lot of things on the way down the slab though... alternatively, worth letting the National Trust know (since they own the cliff)?