marksp : "There is a business case to be prepared.....costs v expected benefits." This is precisely my view and what I have been trying to work towards.
Your point about the difference between doing a job badly and being legally negligent is spot on; it would be the key question Greene would have to address in assessing the prospects of a successful claim. But the claim would not be on grounds of inadequate due diligence; it would be on grounds of issuing those two key RNSs without having taken adequate steps to ensure they were accurate.
I am most interested to find a serious poster who believes Lambert may be real and more than just a Delaware nameplate. If that is so, it changes all my ideas, or rather, it might do; could Lambert be forced to pay for its shares now, given that Langbar is exposed as a fraud? I think not; which would leave us in the same position as if Lambert is a nullity.
nav1000 - presenting a bankruptcy petition against Pearson would not cost much, a few hundred pounds. It's only the petition against Langbar in Bermuda that would cost a fortune in itself. Unfortunately it would not be enough just to tell the Court you held Pearson responsible for your Langbar losses; you would need a judgment, and that would cost.