The circles showed in this vid are relatively simple and mostly obviously man made.

Do you think these blokes in this video are able to create a 'circle' like this:
[link to www.zefdamen.nl]
over one night.?

Or this one:
[link to www.sunstar-solutions.com]
?
This feat seems beyond human ability to produce over one night.
Something to ponder, if this formation was man made allowing for time to get into and out of the field under cover of darkness the construction time left should be around four hours. Given that there are over 400 circles some of which span approx 70ft in diameter that would mean that one of those circles would need to be created every 30 seconds and that's not even allowing any time for the surveying, purely flattening.

I do not know the explanation, but this seems to be impossible to be man made over one short night.