Perjury - lying in court carries up to 10 years in prison. They must have lied to get subposmaster / mistresses put in prison, so the execs should face 10 years for a start, it is a shame we don't have consecutive prison terms as some of them should be facing the rest of their pathetic lives in jail for what they have done.
I still think we should open up a few open cast mines, surround them in fences, barbed wire, and armed guard towers and force these lying / corrupt scumbag execs to life ( until they die ) to hard labour smashing rocks or similar.