Hell Hath No Fury

In his autobiography Clinging to the Wreckage the playwright and former barrister John Mortimer tells how when he was practising at the Bar in divorce cases he acted for a husband whose wife's lawyers repeatedly alleged that the husband had a concealed source of income which could be used to provide additional maintenance payments. The man repeatedly denied this until after persistent probing he at last admitted that he had such a source but claimed that it was covered by the Official Secrets Act and could therefore not be disclosed. Urged to confide in his counsel he finally revealed that he was a part-time hangman at executions. Mortimer a lifelong opponent of capital punishment refused to act for him any further.
Such extreme ethical problems are unlikely to confront advisers today but people do sometimes own up to concealed sources...