COG1 writing to old address

It says on the COG1 form that if I apply to change my contact details you will write to old address to check that the application is genuine.  The people at our old address/es don't know us and have no forwarding address for us. Do they need to reply to you?  Not sure what they will do with the letter when they receive it and I'm a bit worried about strangers receiving info about me.  

Can you explain how this bit works please?
Thank you
 

Dawn - recipients of any notification should do as they would re any post received and which is not for them by name - return it advising that the addressee has gone away for example. They should not open it 
We must carry out a variety of checks to confirm such applications are genuine. 

Thank you.  I understand why you need to do this, I'm just worried what might happen if they throw it away. I know they shouldn't but they might. Maybe I'm being over anxious.

Dawn - totally understand your anxiety and I guess the only way to manage post to your old address is through a Royal Mail redirect. The same issue applies re any post received and in my personal experience most will mark it return to sender in the old fashioned way.
If not then presumably it would go in the recycle bin or shredder which is a more modern approach at times
You are right to ask to allay your own fears but it's not something you can control sadly so I'd suggest accepting it for what it is and to continue to be careful re your own information etc as well. That approach is always the best defence when feeling anxious

Thanks Adam, I'm sure it will be fine.  Form posted off today.