Why Green Tomatoes?

I've been trying really hard with these tomatoes. I've watered them every other day, faithfully, and fed them each time too. They sit in full sun for much of the day, in a sheltered position.

There are plenty of flowers...



...and quite a few fruit but none of them are showing any signs of reddening.



So why are they not ripening, gardeners?



I don't think this peahen is helping but she's probably not the cause either.