In reply to cider nut:
For an international slant (although I suspect you are narrowing things to UK and adjectival grades)
http://www.stanford.edu/~clint/yos/hard.htm lists these first routes of that grade or higher to french 6B as:
6a- (5.9, DDR VIIb) 1906 Teufelsturm Elbsandstein Oliver Perry-Smith, W. Huenig, Rudolf Fehrmann
Note: another grade VIIb was done a few days earlier, but this is the more famous route.
6a+ (5.10a, DDR VIIc) 1910 Grosser Falknerturm, W. Route Elbsandstein M. Matthaeus, Oliver Perry-Smith, H. Wagner
6B (5.10b/c/d) 1938 ? Fontainbleau Pierre Allain
After that according to the list the US leads the way until the mid 80's and Gullich arrives on the scene.