Private landlords

Hi,
About 3 years ago one of the private agency I rented with didn’t pay back my deposit. I chased them for quite a while. They refused to give it back. Then their office was also gone. I went back to my home country. Now I’m back and would want to know what are the rules by government if private agencies don’t pay deposit back? Is there any chance to get my money back after 3 years?

Does the agency still exist anywhere? Do you know the limited company name or number?

I’m not sure if they still exist. It was called sterling de vere. Their office was on Chrisp street London. Deposit was £700-750