Could this be a willow warbler? Smaller than a Robin. Plain chested. By a pond (London park) alone, very loud singer. 7am. https://vimeo.com/520051324
thank you
Oh now I’m confused - here’s a recording of what I thought was a Wren, and it is too different to be the same bird. What could this be? https://vimeo.com/520064700
That is a Wren but it's an alarm call. Quite different from its song
This is the typical song of the Wren so you can judge for yourself
Play this audio clip
Frank Lambert, XC623588. Accessible at www.xeno-canto.org/623588