Prisoner of War records WW1, The Red Cross

[Margaret in Burton]

I've recently been watching My family secrets revealed on Channel 4. More than once they have stated that the Red Cross records for POW's is a brilliant source of information.

Where can I access these? I'm searching for Peter Henry Harrison (sorry Merry). We know he was a POW in Germany in WW1 from 1915 onwards as we have a photo of him in the form of a postcard sent from there. If anyone wants to see the reverse of this with the address of the camp please pm me. It's hard to read, it's written in pencil, and I would have to email a photo of it.