I would have thought that direct-entry Captains, as PL propose, are incompatible with a master seniority list.
Not at all in fact. The theory is that Project Lauren will be open to a bid from all current BA mainline pilots, for either seat. If not enough suitably qualified people bid internally, then flight crew (including Captains) will be recruited externally. The big advantage for new PL recruits is that when they achieve appropriate seniority, they'll be able to move to mainline if they so wish.
In the meantime, it just requires Willie Walsh to appreciate that he's careering down a blind alley by trying to force this issue.
