This morning I suddenly thought to myself that Rupert Graves is the only name British actor I can think of offhand who was in Marple but not Poirot (there are probably plenty, but it would take some work to come up with a list on my part), only then as I thought about it I realized he actually wasn't in Marple: he was in the episode of Morse ("Happy Families", 1992, says IMDb) that is similar (maybe it's just the setting??) to the 2007 tv version of Ordeal by Innocence (the one with Juliet Stevenson, Ewan McGregor's uncle, Jane Seymour, Julian Rhind-Tutt, Richard Armitage, and a baby Gugu Mbatha-Raw).
IMDb also informs me that "Happy Families" is the episode of Morse with Anna Massey, who also memorably starred as a completely different character in Lewis episode 1x1 "Whom the Gods Would Destroy", the one where Anna Maddeley spends her whole life with an assumed name and then becomes a nurse in order to marry this guy just so she can get revenge for his accidentally killing her mother, a prostitute, while he was high during a hazing ritual at Oxford in a weird orgiastic Classical-inspired sex club presided over by Anna Massey; but earlier in the episode she performs an emergency tracheotomoy to save him from choking, which convinces him that she truly loves him after all rather than being a gold digger, just so that it will hurt more when she orders his dogs to kill him. (I am quite fond of this episode and my only regret is that she doesn't get away with it - well, that and the animal cruelty obviously.)
For the most part, Morse was even more hilariously like... that than Lewis, so it's sad that I can't remember what happened in "Happy Families"; maybe I'll watch it again.
The plot is quite different (and honestly, better), but there was a Nero Wolfe novel where a bunch of members of a secret society all thought one of their number was killing them off one by one because it was their fault he ended up in a wheelchair and with chronic pain, and he just encouraged this belief because he hated them, even though he didn't do it. (That's the similarity to "Whom the Gods Would Destroy", which does start out that way before Anna Maddeley kills him too.) But in this case, the setup was a red herring and it was actually someone else, and the grumpy wheelchair user survives, which he did, in the Wolfe book, deserve to do (he was much worse in Lewis). I often think the world of Morse and Lewis is essentially a world made up of parody of golden age detective fiction, and it has a heightened reality and lots of literary references and stuff like that floating around in it as a result; and the world of Midsumer Murders is a further level of parody beyond that, all the way out to farcical levels. So I'm sure there's been at least one episode of Midsomer Murders that's used a similar idea, but it's been a good ten years or so since I watched it I think, and I can't remember anymore, sadly.
IMDb also informs me that "Happy Families" is the episode of Morse with Anna Massey, who also memorably starred as a completely different character in Lewis episode 1x1 "Whom the Gods Would Destroy", the one where Anna Maddeley spends her whole life with an assumed name and then becomes a nurse in order to marry this guy just so she can get revenge for his accidentally killing her mother, a prostitute, while he was high during a hazing ritual at Oxford in a weird orgiastic Classical-inspired sex club presided over by Anna Massey; but earlier in the episode she performs an emergency tracheotomoy to save him from choking, which convinces him that she truly loves him after all rather than being a gold digger, just so that it will hurt more when she orders his dogs to kill him. (I am quite fond of this episode and my only regret is that she doesn't get away with it - well, that and the animal cruelty obviously.)
For the most part, Morse was even more hilariously like... that than Lewis, so it's sad that I can't remember what happened in "Happy Families"; maybe I'll watch it again.
The plot is quite different (and honestly, better), but there was a Nero Wolfe novel where a bunch of members of a secret society all thought one of their number was killing them off one by one because it was their fault he ended up in a wheelchair and with chronic pain, and he just encouraged this belief because he hated them, even though he didn't do it. (That's the similarity to "Whom the Gods Would Destroy", which does start out that way before Anna Maddeley kills him too.) But in this case, the setup was a red herring and it was actually someone else, and the grumpy wheelchair user survives, which he did, in the Wolfe book, deserve to do (he was much worse in Lewis). I often think the world of Morse and Lewis is essentially a world made up of parody of golden age detective fiction, and it has a heightened reality and lots of literary references and stuff like that floating around in it as a result; and the world of Midsumer Murders is a further level of parody beyond that, all the way out to farcical levels. So I'm sure there's been at least one episode of Midsomer Murders that's used a similar idea, but it's been a good ten years or so since I watched it I think, and I can't remember anymore, sadly.