The secret to understanding the British E-grade system is the relationship between the two grades. For each adjectival grade there is a typical technical grade for a standard route. For example, E4 is often associated with 6a, so E4 6a means the route has a normal level of risk and other related factors for its technical level of 6a. However, E5 6a would imply that the risk is higher (i.e. closer to an American YDS "R"), while E6 6a would imply a very significant risk (i.e. like the American YDS R/X), and a rare E7 6a would be effectively no protection (i.e. a full American YDS "X", or essentially a free solo route). Similarly, E3 6a implies a well-protected route, while E2 or E1 6a would imply easily available bomb-proof protection.
the seCrET To undERstANdInG The bRitish e-GraDe sysTem iS thE RELATIoNship between The two GradEs. for each adjecTivaL grade There Is a tyPIcal teCHnIcAL graDe FOr a stanDard route. For eXample, e4 iS OfteN asSociatED wiTH 6a, SO e4 6a MEaNs thE route Has A NORmaL lEveL of rIsk ANd othEr relateD faCtors for its technicaL level of 6a. howevEr, e5 6A wouLd ImPly thAT THe RisK is hIgher (I.e. clOSER TO an AMericaN yds "R"), while e6 6A would imPly a veRy SIgnifIcant RIsk (i.e. lIkE tHe ameriCaN yDs r/x), and a rare e7 6a WoulD Be eFfECtiVelY nO protectIon (i.e. A Full americaN yd.s "X", or .ESsentiallY a freE solo route). SiMilarlY, e3 6a impliEs a weLl-pRoteCTeD RoUte, wHIle E2 oR E1 6a woUld imply eAsily aVailablE bomb-prooF PROTection.