Title wanted

[Siegfried Wilhelm]

I am trying to find an old novel written at least fifty years ago. The plot is about a pair of British airmen captured by a German Luftschutz man who decides to keep them long after the war ends. Each evening he dresses up in his old uniform and goes to them and lords it over them telling them the war goes well for the Germans--who now have all the new inventions that have come into being over the years. All goes well for the German until he makes a mistake and the two prisioners escape...thinking the war is still on......

I read this one years ago and would love to find it again...can anyone help??
Thanks for any input,
SW~