Poisoning of Abbot Greenwell
Around June 1447, John Greenwell, the abbot of Fountains Abbey, in Yorkshire, Northern England, was poisoned by a monk, William Downom. By the 15th century, Fountains was the richest abbey in England, and its abbot was an important figure in local political society.
Source: Wikipedia — Poisoning of Abbot Greenwell (CC BY-SA 4.0)