In reply to mr.sheen: Returning to Mr Larssen, the basic thing he doesn't get is that French grades are 1-dimensional (6a, 6a+ etc) whereas UK adjective/tech grades are 2-dimensional...
VS 4b 4c 5a
HVS 4c 5a 5b
E1 5a 5b 5c etc.
This means that regardless of what the various grades describe, it doesn't matter what you do, you're never going to be able to properly map French onto UK. The best you could do is map various French "grade lines" onto the UK "grade area".
It might be possible to map the US 5.nn R/X type system onto UK because with the addition of the R/X suffix it has become 2-dimensional. However the 2 dimensions are different to the UK ones so it would be a bit difficult.
This is apart from all the problems that have happened by compressing too much into the higher UK grades - both adjectival & tech.
Connected to this is "grade width". To my mind if the majority of climbers (say maybe 80%) can agree that route B is harder than route A (for adjective and/or tech), then route B should be a higher grade than route A. This hasn't happened with UK grades which are generally too wide. This has allowed/necessitated graded lists to appear - although they're a lot of fun for discussion in the pub.
Also, it's a shame that the UK grades didn't keep one tech grade step for each extra E grade (mid-point: E2 5c. E3 6a, E4 6b, E5 6c, etc). This would have made it more usable.
Unfortunately, I think it's now too late to fix the UK grade problems. Luckily, this only happens above my level so it doesn't directly affect me
End of essay.