Apparently the investigation was launched due to the result of the information provided by the inquiry led by Sue Gray.
It is a bit of a double-edge sword. Individuals will be interviewed and if found guilty fixed penalty notices could be given - that's good. On the other hand it means that Sue Gray's report will be delayed. Unfortunately it now muddies the waters somewhat, it got to the point where it should have been one or the other.
The Met's hand looks to have been forced by recent events, and that is a shame. It could have taken the lead ages ago when the evidence broke and thus obviated the need for the Sue Gray inquiry.
But get this: The PM says he is "willing to be interviewed by police".
Since when did a citizen get the choice to be interviewed in a police investigation? He has the right to remain silent, but that has ramifications and could prove problematic at a later date.