Originally Posted by Chris T

I think you can assume that a debt recovery agency used by a major company like NTL will not employ Ronnie and Reggie style tactics. Your kneecaps are probably safe.

What is happening now is that the debt recovery agency is trying to track down the former occupier of the address, who still owes money. A standard part of their investigation is to write to you, the new occupier, to see if you have any information that might assist them. You are not under any obligation to give them any information. The debt is not secured on your house or anything else you own so they can do nothing to you. Even if they thought they could, they would have to go to court before they could take anything off you!

You could just ignore the letter but if you want maximum peace of mind, and you know the new address of the former occupier, then why not just grass on them?