Old Harry's Game is a BBC radio comedy starring the Horned One himself, Satan (voiced by Andy Hamilton), as he deals with the trials and tribulations of being the only competent hellion in an infernal bureaucracy. The show ran from 1995 to 2012, with large gaps between series and specials. The show has seven seasons-- sorry, "series", a Christmas and New Year special or two, as well as a 2012 Olympic special.
In the first four seasons, the world-weary Satan is pestered and challenged by The Professor (James Grout), a very moral atheist who's initially new to hell who takes to challenging Satan's perspective that all humans are innately evil. Complementing the Professor is Thomas (Jimmy Mulvile), a selfish, arrogant, irredeemable bastard who occasionally shocks Satan with his horribleness and makes a good case for Satan being right. Thomas is actually responsible for the car crash that killed the Professor, so of course Satan has the two rooming together. Satan also has to deal with his treacherous demonic assistant, Gary (on whom Thomas is a bad influence) in the first season and, in later seasons, his new assistant: the doggedly loyal and distinctly un-demonic demon Scumspawn (Robert Duncan), who is the only demon in hell to ever donate to a donkey sanctuary.
In his efforts to prove to the Professor that humanity is evil (and to generally just mess with him), the first few seasons have the show focus on a cavalcade of historical figures who turn out to be nothing like their legacies would indicate. In the second and third especially, the main plot thread is a bet between the Professor and Satan: if the Professor can prove that humanity is mostly good (including Thomas), then Satan will let the Professor and his still-living widow Deborah be roomed together in hell when she inevitably dies.
In season five, Satan leaves hell and tries to convince the world's leaders to be more virtuous and holy because Hell is suffering from a serious overcrowding problem, which was referenced in earlier seasons in passing. While Satan is out and about trying to get more people to go to Heaven, Scumspawn is left "in charge" of Hell where he is woefully incompetent and far too much of a pushover-- which makes sense as Scumspawn is the only demon in Hell who collects furbies. Most of the time, Scumspawn enlists the help of Thomas to stop whatever is going wrong, but usually the two fail together and it's not until Satan is home that they get things sorted out.
It is notable that this is the first season without the Professor, as the actor playing him had to leave the part for health reasons. The Professor's absence is commented on and explained in-story.
Season six has a new character replace the Professor: Edith, who is another academic and also Thomas's former mother-in-law. The two hate each other immensely as Thomas was (to put it gently) a sub-par husband to Edith's daughter. So of course Satan has them staying together. Edith is in hell because she supposedly committed suicide, but she insists she was murdered. She is as insufferable to Satan as the Professor had been, but she's also a good writer, which leads to Satan offering her a deal; he'll find out how she really died if she writes a biography about his life in order to get his side of the story out to complement the Bible. Edith agrees.
In the final season, God (who has been portrayed as an arrogant and fairly unlikable jerk), has finally gotten bored with creation and has left. Angels are now running Heaven, but their computer system is all messed up, resulting in people being sent to Hell who legitimately do not belong in Hell, even by heaven's high standards. This includes a dog, Scamp, and a baby later called Patrick. Much of season seven revolves around the characters bribing, begging, and threatening angels in effort to get the baby out of Hell, then again out of Heaven when its revealed that time doesn't pass in heaven, and that Patrick will remain an infant forever (which horrifies Edith).
The show is hilarious, and can be found on itunes.