I lent my ex-partner a sum of money to pay off a (sort of) debt in September 2019. I have lent him before and he has paid me off as a lump sum at later dates so, foolishly, I didn't get any form or written agreement.
Recently, we split up without him having paid back this money. I intend to ask for it back but how should I go about legal action if he refuses, and what are the chances of recovery?