Locked Out From Site

Hi there, a client of mine had a site built using WP – the designer has gone out of business and cannot be reached. My client is unable to access the site as the email address used to reset the password is no longer in use. I would have used the database to regain access but the old designer is hosting the site and moved countries and is no longer answering emails.

Does anyone have any ideas how my client (who owns the site/domain) can regain control?

Many thanks