After the Sue Gray enquiry there will be a Metropolitan Police investigation. There are a couple of high ranking Metropolitan Police officers related to Cabinet members. Then when no evidence of law-breaking has been found there may be a Parliamentary Select Committee enquiry. Such a committee will have a majority of it as Conservative MPs. This sort of enquiry can go on indefinitely.
Nowadays we must regard 'Yes Minister' and 'The Thick Of It' as utterly mundane.