Yes R20 - I know
I was merely explaining why the prewar/early wartime 2nd Pilot was often the Navigator on multi crew aircraft - because the RAF was extremely short of qualified Observers/Navigators.
Ian Blair was included for interest and to reinforce the idea of the shortage of trained/qualified Observers/Navigators.
After 1941/42 large numbers of Observers/Navs became available as the training schools got into gear.