Around the time of Coventry British Jamming of the German blind
bombing system was mostly ineffecvive despite claims to the contrary.

Source, please?

Mike, Knickebein (SP) most certainly was jammed - I've interviewed KG airmen
that rode 111s, 88s, and 217s during this period and the jamming was hit or
miss, but definitely it worked on occasion. The 'Wizard War' was active almost
from the first siren of the conflict.

v/r
Gordon