Hi all, maybe this is common knowledge, but where we sat in the Embassy today there were at least three of us who were surprised to find out that we should have had with us a series of photos of our young children, to show how they'd progressed from the tiny under-five in their original passport photo to the bigger child they are now.
The agent at Window 1 printed the stuff off the web to prove that yes indeed it is clearly stated on the first page of the instructions on the London Embassy web page, but there are two problems with that: if you google your instructions, you sometimes get old web pages that haven't been removed, and also you can get instructions on what looks like the very reliable travel.gov site - which doesn't mention it at all.
Fortunatley we were able to cobble together a collection of photos out of my husband's wallet, which looked enough like each other to prove that she's our girl and has been all along, but it was a close thing for a little while, and just caused too much unnecessary stress.
So now you know! Hope that saves some others unnecessary trouble in the future! :-)