It was the compere/bingo caller - can't remember the character's name, sorry.
He meant to poison Jules, played by Russ Abbot. He used rat poison, he just wanted to make him a bit sick but Bunny, played by Ernie Hudd deviated from the usual skit and drank the wine when it was always Jules who drank from the bottle. Because Bunny wasn't in good health & like a bevy or two, the rat poison killed him when it would only have made Jules sick for a day or two.
The younger man dreamed of being a stand up comedian, he approached Jules with some of his work but he discouraged him & verbally tore his work to pieces rather then encourage him so he wanted revenge.