It would depend on the date of any wrongdoing, found by their investigation. I believe they are already barred from bringing charges for any alleged misconduct before November 2016. The longer they take to find anything, the less chance they have of bringing a case against us, because we have been very clean for many years now. If there was any wrongdoing by us, I suspect it was well before 2016.
This is unless the PL regulations can somehow circumvent the Limitation Act 1980, maybe with their own version of limitation.