It’s now been a week since I introduced the rooster to the hens and there has been no action whatsoever. He is right at the bottom of the pecking order and the newest hen who used to occupy that position seems positively pleased that she has now got someone else to pick on.
Day by day he gets more confident and last night he slept in the same manger as the other three so who knows.
I noticed that there was a blood spot in one of the eggs that I cracked yesterday when making some aioli and wondered whether this was in fact the first sign of fertilisation. After exploring a bit on Internet I read about candling the eggs to see if they had been fertilised.
So armed with a torch I looked at the eggs.

The weird light effect is just the surgical glove I was wearing but you can clearly see the air sac at one end of the egg
To candle an egg, turn off the ligths in the room and hold the egg over a torch. I used one of those pocket torches with LED lights. If the egg has been fertilised, you should see a more opaque area. Mine all look the same so it looks as though they haven’t been fertilised yet. Or I’m looking for the wrong thing.
Unfortunately, it is impossible to know whether the egg is fertile so early on. The embryo only starts developing once the mother hen starts sitting on the eggs.
The only way is to crack open the egg as that way you can see the cloudy sperm in the yolk.