This was doing the period of Edward I? He expelled the Jews from England, in part to steal their wealth and void his debts to Jewish moneylenders. I believe he also got clerical blessing for doing this as it did allow Jews who apostasised to remain providing they surrendered almost all their wealth.
The money and other salables stolen from the Jews aided Edward in financing his wars in France and Scotland.
1190? Richard Lionheart.
So instead of expelling a few, they threw them down a well. Save time and effort. More fun for the mob, and mobs must have their fun.