Yeah he said that she emailed him saying a letter had turned up and she said it looked quite important think had the police force name on it so she opened it, then she scanned it and sent it to him, she said that she's not been another letter but she can't be sure so we are taking it that it's the first one.
Bit annoying as I get the feeling she opened it to have a nose and find out some dirt rather than help him, as she could have forwarded it to him still sealed or as you say return as 'not known'.
If it was me I think I probably would leave it and let them find my correct address as there all up to date, but hes not that sort which is why I think he wants to get it sorted so it's not hanging over him think he is going to phone his agency see if they can trace the other guys down and in meantime draft a letter to send back, thanks for all the suggestions guys appreciate the help so far.