The Aldersbrook Cuckoo

A repeated "peeping" noise greeted us as my wildlife photographer friend left my house this evening just before 7pm. Neither of us recognised the bird making it, and although I looked, I couldn't see it. The rain didn't help.
Fifteen minutes later, a neighbour who has a good knowledge of birds called to ask if I knew what was making the sound, and he spotted what he thought was a cuckoo sitting in the oak tree immediately in front of my house, by Wanstead Flats. I grabbed binoculars and a camera, confirmed it was a cuckoo, and started trying to get a record photograph. Just then, my next door neighbour asked if we were looking at the cuckoo! That surprised me somewhat, as I hadn't known he either had an interest in or a knowledge of birds. He has certainly got the knowledge, though - as he drives a taxi.
He explained that he knew what it was because he'd found it on the pavement in front of the shops at the corner of Aldersbrook Road and Wanstead Park Avenue. He could see it was a young and distressed cuckoo, he said, so he'd picked it up, put it in his cab, brought it home (the other side of the Flats) and released it by the oak tree. From there it had fluttered up onto the branches. He then called the RSPCA who advised him to put it back near to where he'd found it, but this was to prove impossible as by now it had ensconced itself on a branch, making these most-un-cuckoo-like sounds, and was impossible to catch.
I was able to see it quite clearly from my upstairs window, albeit by now the rain was beating down and it had tucked its head in, and had stopped peeping. The magpies had stopped harrying it, too.
Considering the scarcity of cuckoos in this (and other) areas - only one having been reported locally this year - finding a fledgling by Wanstead Flats is quite amazing. Unless it had been carried there by another taxi driver, one must suppose that it had bred locally - possibly to a local Dunnock - but of course Reed Warblers were heard on Alexandra Lake earlier in the year. Who knows.
My fear, though, is that it appears to be very young, and that it will not last long having been removed from the possibility of being rescued and cared for by its foster-parents - whatever they are.
Paul Ferris, 18th July