My older brother was a BE Air Radar Mechanic trainee at Cosford in 1961/62 and he told me that according to their instructors we'd sent in Victors at low altitude as well which successfully penetrated the US defences because they simply never expected a low level strike and their air defence radar wasn't set up for one.
Talking to a guy from Strike Command Bombing School when I was a Lindholme in 1973, he told me that Chapman Pincher had gone along on one of the attackers but I don't see how this was possible unless they 'dropped' a crewmember.