Mr Chatterjee is the owner of Speedy's Cafe. Mrs Hudson meets Mr Chatterjee at the cafe and they have a romantic relationship. He also offers to take her on a cruise.
However, Sherlock deduces that he has a wife in Doncaster, which upsets Mrs Hudson and after confirming it she has a argument with Mr Chatterjee. According to Sherlock, he has a wife in Islamabad as well.
However, at John and Mary's wedding Mrs Hudson is with a man who is hinted to be Mr Chatterjee.
Mrs Hudson with Mr Chatterjee?