I posted a link to the legislation, but in case you haven’t looked at it, this is what I had to say previously. This is all in the context of what is written into legislation. Do click here to see the broader post:
The fourth condition is that he [the Nominated Officer] does not make the required disclosure to … the Director General of the National Crime Agency as soon as is practicable after the information … comes to him.
Emphasis again mine. My reading is that, again, this would preclude investigation. Case law would be required to confirm this - the prosecution would likely argue that suspicion was required to investigate, therefore confirming guilt. The defence might state that there was potentially suspicion but that additional information was required to confirm it.
Basically, it seems that the legislation doesn’t give banks scope to independently ask questions (i.e. investigate) if it seems there is already ‘information’ that falls under scope of the reporting obligation to the National Crime Agency.