The difference between activism and class actions seen in the US and the traditional UK approach of 'you win some, you lose some' has never been more starkly shown as by the woes of Carillion.

While institutional investors sold to minimise their losses as they saw the bad news unravel, had this been a US company you would have seen class actions aplenty.  

However, the bigger issue here is about the approach of institutional investors selling in silence and the less sophisticated investors who now will receive nothing.

Should the FCA , government or auditors (internal and external) have said more?  What should the company and board have said?

Blaming a bad contract in Qatar seems too simple.  Creditors, pensioners and employees are all going to suffer here while institutions got out, even with a reduced gain or loss. 

This needs further and detailed review as to the adequacy of financial reporting, which seems lacking here.