In terms of the field of major crime, in particular homicide, yes, it is. It's acknowledged as good practice. Normally from within the force, so if it's a conventional murder, you would put together a review team within your own -- from within your own force and ensure that structural governance wise, leadership, all the usual issues, that you would undertake that review.
In a more serious case, you may commission an external chief officer to lead a team. This was slightly unusual in that Mr Hogan-Howe asked me to head up a team into something that was major crime but wasn't a homicide. So it was slightly new ground for the Police Service, but for very, very good reasons.