So, plan C was to separate off the breeding girls (Barbara, Ann, Pong, and one of the Harem girls), and to put Bertie in with them for periods of time but not to leave him in there overnight. Immediately we separated them, Ping got distressed (presumably because she couldn't get in to her usual nestbox), and Bertie got indignant. He called, and all his ladies came running, lined up against the fencing that separated them.
Bertie showed no interest in any of the girls. We put Ping back in with them, and went home. We came back later that day to let Bertie out and to check on the girls. As soon as he was back with everyone else he humped everything in sight.
There were 3 eggs, including one each from Ping and Pong. We collected them, and broke them at home to see what was going on. One egg - we don't know which of the other three laid it - was definitely fertilised, it had the tell tale white bullseye ring. One of Ping/Pongs was definitely not fertilised. And one had a white bit (as many eggs do) but I couldn't be sure it was a bullseye.
Since then, every other day, we've shut Bertie in with the 5 breeding girls in the morning, and let him out in the afternoon. The idea is that the breeding girls don't have to put up with him all the time, and he he can still keep control of the main group. We were going to put him in every day, but we were sort of hoping that a day's absence from the breeding girls might make him fonder.... but we haven't seen any evidence of that.
Still, we've collected a number of eggs, although we haven't tested any more for fertility. The plan is to incubate all the eggs, even if it means 2 incubators, and then remove the clears at Day 7 when we candle them.
That's the idea, anyway.
We're planning to put them in the incubator on Saturday.