In reply to Michael Gordon:
> (In reply to Alan James - UKC and UKH)
> [...]
>
> Don't think so. Quite a few folk seem to just do it alphabetically - admittedly this probably causes rather than avoids confusion!
As the most prolific CC editor over the last 20+ years (and stemming from the two Cordee Wye Valley guides before that) I have adopted the following system:
The first named is presumed to have led the whole climb unless there is the qualification AL or VL. If AL is used, then the first named led the first pitch and then the climbers alternated. If VL is used the sequence may be not known or not consdered material. If any of this does not reflect fairly the relative effort or achievement there is always the option of adding a comment such as 'X led the crux pitch'.
Because some first ascensionists and past guidebook authors and editors may have used different formulas, there is no guarantee that the lists will always be wholly accurate, by these principles, or in other respects. The records can only be improved, as Alan says, by people writing in when they know of or spot errors. Both UKC and the CC (for its own guides) have online facilities to do this, which removes one of the problems of the past in such messages not getting through to the compilers of the next addition. It may, of course, be some time before the correction appears in print or even online.
Another point: the leader is presumed to have climbed in the implied style, but the second may not have.
Sometime it may be worth discussing whether strings of tiers-on to FAs of ground-level-starting, single-pitch routes, especially sport climbs, should all be credited. And then there is the new qualification LL (both led or all led) which have allowed myself to be cajoled into adopting, against my better judgement.