Straccaletto
We file an 'overload' as part of our Mandatory Occurrence Reporting scheme which requires us (and you?) by law to report any incident in which the safety of an aircraft was - or could have been - endangered.
Thus if a controller feels that he was so busy that it was dangerous, an overload is filed.
The problem is that regardless of the spokeswoman's comments to BBC, the fact is that most controllers have experienced being dissuaded from filing overload reports rather than being encouraged to file them.
The reasons for this are not difficult to guess: someone screwed up the flow rates, management don't want to bust their targets, don't want to drop a collegue in it, can't be bothered with paperwork.
Unfortunately we still have a 'blame' culture rather than one where the overloads could be analysed to determine problems that need fixing and/or used to communicate among the workforce such that we can all learn from the unfortunate experiences of others. In the reports I've filed, if you get any feedback at all, it is generally of the type 'sector x controller mistake and appropriate remedial action has been taken'. Which is nothing more than a convenient statement and as a result nobody learns anything at all.