Wrote an application for a friend. Who is the owner of the software? [closed]

Question

Friend asked me to develop a software application for him. I did and he paid me. There was no written contract. I live in UK and he resides in Canada.

My question is: who is the owner of the software now? Can my friend make and sell copies without my permission? Can I do the same?

I'm asking this because another person also wants to buy it, but friend insists on receiving some kind of sale commission, because the software was originally written at his request.