One of the primary reasons why people stay addicted for long is to win big. They think a big win will solve financial and all other problems in their lives.
For this very man greed was his problem £20000 is a huge sum that can afford a very lucrative business. Giving such huge amount on gambling shows his high level of greed and people of this kind can do anything just to make money not minding if it's legal or not. I wish he recovers soonest because this can cause a man to commit sucide.