Update at 12th April: judging by lots of helpful comments to this blog, the incubation period seems to be going smoothly despite some unpleasant easterly winds which have blown directly into the nest platform.
If you don't live within reach of derby, or even if you do, David's book, Tales from Concrete Jungles (see here) is available in kindle and hardback versions. It includes a few pages about David's 2010 visit to Derby and his encounter with us and with our project.
Some screengrabs have been sent in by Wendy Bartter, Yvonne Harvey and Helensara to whom many thanks.
Now the long incubation period starts in earnest and will last for about 30-33 days. Hatching will take place hopefully in early May.