Purpose of inquest?
Nigel,
I believe that the purpose of an inquest is solely to determine the cause of a death. In Scotland the rather more descriptive "fatal accident enquiry" fills the same role.
There may be a secondary opportunity to advise on lessons for the future and to spot trends to similar incidents in the past, but that's not the prime concern. I'd say an inquest is much closer in goals to a board of inquiry/accident investigation than to a trial, but the inquest is more narrowly focussed on the death, rather than building up a whole picture of an accident.
There's a lot of flexibility in the approach the coroner takes to consider wider issues. In a complex case like this, the coroner will be seeking to decide whether there is sufficient evidence to rule it was an "unlawful killing" or an "accident", or if the cause remains "open".
If it's "unlawful killing", then some sort of police investigation would be expected. It's also possible for an inquest to come to different conclusions from an inquiry, perhaps consistently, because of its different emphasis.