Without wishing to take sides, and, like everyone else I have very few "facts" on this matter, only what is reported, but I do have one major problem with one of the answers given thus far.
Several folks have commented along the lines of "if the Met suspected a crime was being committed then they have to respond" - a statement that, on the face of it, I have no problem with ..... However .....
How would they "suspect a crime was being committed" unless someone told them

AFAIK the Met are not clairvoyent .. therefore they were told, by someone.
The BIG question is by Who

and Why

It is the answers to those two points that really matters .. IMHO
If it was done by Powers within the present Government in order to embarrass/shut up Her Majesty's Opposition then it is exceedingly dangerous.
If it was done by a minor Civil Servant who didn't like his work being made common knowledge, then the "wait and see" approach is entirely reasonable.
The problem is .. will we ever know the difference or the truth
