The two cockerels I kept (a leghorn and an ancona) are shaping up nicely, and both are obviously fertile (with blastodiscs inside every egg). I'm happy with their size and growth, so I feel they haven't been set back too badly by the lupins.
Here they are having an afternoon singalong.
If the experiment trying to cross a layer type with the meat birds fails, I'll probably pick up some more leghorns and put them in with the white chappie above. Leghorns are notoriously flighty, and most people find the white ones boring (these were the original dual purpose birds when industrial chicken farming began to take off), but I like their looks, and find that they readily tame down when treated properly. They're still flighty when something flails or bangs, but this is a useful survival instinct when goshawks are around. Best of all, in my experience flighty males only rarely turn aggressive toward their keeper. It can happen with leghorns, but it isn't particularly common.