If a couple are separating/separated or divorcing/divorced, I would expect the firm to owe the same duty to each of the couple as they would to any other client, which would include confidentiality over the matter upon which they are to be instructed.
As it is unlikely one firm would act for both parties in the divorce, I question whether it would be appropriate for the same firm to be advising both parties on their wills. It may be straightforward, but you will only know that to be the case with the benefit of hindsight.
Once the divorce is finalised, and provided there are no ongoing matters to be resolved, I would have thought the firm could act for either party without needing to inform, or obtain the consent of, the other party. Even then, it might be prudent for separate individuals within the firm to advise the parties (especially if the breakup of the relationship was acrimonious). In the meantime, I feel it would be creating a hostage to fortune for a firm to be advising on/drafting wills for either party, who might also be advised by the lawyers acting in the divorce on actions relating to, say, joint property or nominated assets, which could adversely impact the advice given by the will writer.
I wonder if there is any guidance issued by the SRA/Law Society on this aspect?
Paul Saunders