Today we tried slightly different tactics. I was watching them and one Maran was pacing up and down in the run, looking particularly agitated about being stuck inside. So we let them out, and then the girls and I (that's human girls) stood and watched and after a few minutes, said Maran headed off to the hedge at the top of the field and snuck under the fence. I have looked and looked in this hedge but it is very overgrown and fenced off on one side with a wall on the other. Not exactly accessible. Fortunately she chose a spot close to the fence though very overgrown with thistles, nettles and brambles.
At this point we left her to it. Later however when she was still sitting there hours later [is that being broody?], we went over and after a bit of cutting back of the undergrowth, she got up and revealed 18 eggs. I've left two but collected the rest and conducted the float test.
The eggs all passed - eggs stay fresh for ages don't they? I am hoping that she is still going to hang out there because I can reach the eggs and I know where it is. The only disappointment was that I'm not sure if anyone else is hedge-laying - I suspect so, but I can't work out where. Still I think I've got the main culprit. Four chickens have laid in the house so far today.
Now what the hell do I do with all these eggs???