I agree with TM that corporate risk management has failed here but...
If the pilot was licensed, the ac was serviceable and no laws were broken, I think it's a bit harsh to blame [U]StormHarbour[/U].
The pilots made bad decisions in deteriorating weather but what the UK court is basically saying is that you should never get into an ac in Peru as they are all rubbish unless you audit them first.
Even then, an audit would have found an experienced licensed pilot, a serviceable ac and what else... Unless you did the audit on the day of the flight, how could you predict bad weather and the decisions that would follow it? Challenging terrain cannot be mitigated if that's where you are going. Route selection will only do so much.
Clearly if I missed the lack of airworthiness of either pilot or ac, I'll be quiet.