In times of change or uncertainty we all need reference points - a star to guide us by. As you will be planning for the possibility of the UK leaving the EU without any negotiated withdrawal agreement or transition period, one star for directors of companies to follow is their duties as directors under company law.
The Companies Act 2006 codified for the first time what had previously been a collection of common law principles, developed by the courts over previous centuries, augmented by some specific statutory provisions.
Sections 171 to 177 of the Companies Act set out the general duties of directors, including some that are particularly relevant to Brexit contingency planning:
Context is of course crucial. Businesses with substantial trade with Europe, or indeed other parts of the world, and with overseas operations will have had to consider Brexit carefully. Those with the resources to do so may well have put in place detailed contingency planning. For others whose business is principally in the UK, their concern will be more about the macro-economic effect of a no-deal Brexit on their business generally, or the effect of prolonged uncertainty on business confidence and investment decisions.
Mark Twain once said "I have spent most of my life worrying about things that have never happened". That is a comment about the comfort of hindsight - for now businesses have to consider their response to the current political situation, and directors will need to think about their duties in that regard.