Finding the ‘known unknowns’ or, is it the other way round? Whichever but that is the critical challenge for all non-executives. How does one ensure that one is alerted to the ‘black swan’?

It does seem remarkable that the Board of the Post Office was not given or did not avail itself of an opportunity to intervene at an earlier stage. The Public enquiry will doubtless opine and perhaps it is unhelpful to be too specific about this case at this stage. But whatever else, so far as the Post Office itself is concerned their conduct has been outrageous as Sir Wyn Williams found.

But without forming any final judgment on the Board’s behaviour, what and how should the warning signs have appeared on their radar?

Presumably the Board had a risk register. The installation and operation of an IT system the size, breadth and cost of Horizon ought surely to have been included.

The Post Office had powers to prosecute without reference to the CPS. These powers are pretty unique and fraught with reputational mine traps. You only need one court to make a critical statement for it to have real reputational damage. The exercise of those exceptional powers should itself have been something which the Board should have overseen. They would surely have noticed and questioned the contemporaneous exponential rise in the number of prosecutions and closure of post offices.

Both these are matters which the Board should have monitored as part of a risk agenda without any further red flags appearing. Any more evidence of awareness of the problem and a failure to follow up will be uncomfortable for the non-executives of the Post Office to account for.

Given the complexity and commercial considerations of the arrangements with Fujitsu and also with the multitude of sub-postmasters the Board may have been unduly influenced, at least initially, by legal advice.’ Do not admit liability’ we are told when we get out of a car after an incident, even if it was you who reversed into a stationary vehicle! I exaggerate. But there must come a point in such circumstances for the Board to say ‘Enough! There is more at stake here than the bottom line’. Boards need always to be prepared to challenge legal advice on case strategies.

How would your board measure up in these circumstances?