Help please. WW2 French POW in Germany mail via GPO London to France

[dtrapnell]

The attached shows the front of the return part of a form used to send gift parcels to French POWs in Germany. Can anyone explain why the reply/acknowledgement part was addressed via GPO London?
I have seen another similar.
Many thanks & a happy new year to all who read this
David

[Frank Schofield]

David

The UK return address suggests the parcels were sent from the UK (probably by the Free French
Authorities)

Frank Schofield