Luftwaffe fighters stalking B-17's back to Britain

[Broncazonk]

I remember reading something about an interesting mission where a large formation of German fighter aircraft used English speaking pilots (and captured challenge codes) to mimic returning Allied fighter escorts all the way back to Britain and to at least one B-17 base. The plan worked perfectly resulting in many B-17's being shot down (in the landing pattern) and many more being strafed on the ground. I can't remember where I read this however.

Does anyone have the details of this mission?

Thanks!

Bronc